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SDLRC - Index of Diamond Reference Major Key Words


The Sheahan Diamond Literature Reference Compilation - Scientific and Media Articles based on Major Keywords
The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcements called the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The references are for personal use information purposes only; when available a link is provided to an online location where the full article can be accessed or purchased directly. Reproduction of this compilation in part or in whole without permission from the Sheahan Diamond Literature Service is strictly prohibited. Return to Diamond Keyword Index
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
A-An Ao+ B-Bd Be-Bk Bl-Bq Br+ C-Cg Ch-Ck Cl+ D-Dd De-Dn Do+ E F-Fn Fo+ G-Gh Gi-Gq Gr+ H-Hd He-Hn Ho+ I J K-Kg Kh-Kn Ko-Kq Kr+ L-Lh
Li+ M-Maq Mar-Mc Md-Mn Mo+ N O P-Pd Pe-Pn Po+ Q R-Rh Ri-Rn Ro+ S-Sd Se-Sh Si-Sm Sn-Ss St+ T-Th Ti+ U V W-Wg Wh+ X Y Z
Sheahan Diamond Literature Reference Compilation - Media/Corporate References by Name for all years
A B C D-Diam Diamonds Diamr+ E F G H I J K L M N O P Q R S T U V W X Y Z
Each article reference in the SDLRC is tagged with one or more key words assigned by Pat Sheahan to highlight the main topics of the article. In an effort to make it easier for users to track down articles related to a specific topic, KRO has extracted these key words and developed a list of major key words presented in this Key Word Index to which individual key words used in the article reference have been assigned. In most of the individual Key Word Reports the references are in crhonological order, though in some such as Deposits the order is first by key word and then chronological. Only articles classified as "technical" (mainly scientific journal articles) and "media" (independent media articles) are included in the Key Word Index. References that were added in the most recent monthly update are highlighted in yellow.
Major Keyword# Sub Keywords# of References# New ReferencesKeyword Definition
Aboriginal Issues10442Aboriginal Issues involve the native groups in Australia and Canada, and are relevant where their jurisdictions overlap with diamond exploration and development.
Accretion3410Accretion in the geological context relevant to diamond literature refers to the process of adding material to a tectonic plate or landmass either through the collision of plates or through the deposition of sediments along coastlines and riverbanks.
Alkaline Rocks2189112Alkaline Rocks are rocks formed from magmas or fluids enriched with alkalis (potassium oxide and sodium oxide) relative to silica (silicon dioxide). When the magma is under-saturated with alkalis it is called "sub-alkaline". Alkaline rocks can be extrusive or intrusive. Although rare, they form a wide range of minerals. Alkaline rocks are relevant to diamonds because kimberlites and lamproites originate as alkaline magmas. They are especially relevant to rare earth minerals when they occur as carbonatites and syenites.
Alluvials345148Alluvials as a keyword in the diamond literature refers to both the formation of unconsolidated sedimentary deposits through water transport and the diamonds that end up in such alluvial deposits also known as placer deposits. The keyword includes articles about marine diamond deposits.
Basanites3981Basanites are an extrusive sub-class of alkaline rocks associated with basalts formed through hotspot volcanism. Basanites are lower in silica and higher in alkalis than basalt. They are not very relevant to diamonds.
Boninites2481Boninites are an extrusive mafic rock rich in magnesium and silica whose magma is formed in "fore-arc" environments near island arcs where the "mantle wedge" above a subducting plate near the ocean trench undergoes partial melting. Boninites are more relevant to rare earths than diamonds.
Book11043117Most of the scientific diamond references involve peer reviewed articles published in journals. The key word Book refers to a theme based collection of articles by multiple authors or a multi-chapter book by a single author. The references usually include an additional key word that defines the topic of the book. The reference may be about the book itself or a review of the book. The reference usually has an additional keyword that describes the topic.
Boundary101312Boundary refers to both plate boundaries such as occur in subduction zones as well as the transition between mantle regions such as the earth's solid "inner core" and liquid "outer core".
Carbon291984Carbon is relevant to diamonds because that is what a pure diamond is made of, namely an octahedral carbon crystal that forms in a combination of pressure and temperature that does not exist at the earth's surface. The diamond form of carbon is the hardest known naturally occurring material, while the hexagonal crystal form of carbon known as graphite is among the softest materials. Articles with the key word "carbon" encompass a wide range of carbon related topics, of which the most relevant to diamond deal with diamond formation, the carbon cycle within the earth as opposed to the gaseous form of carbon dioxide in so far as the inputs for diamond formation are concerned, and the transition between diamond and graphite as defined by the pressure-temperature regime at the center of which is the diamond stability field.
Carbonado9890A Carbonado is literally a "black diamond", a polycrystalline aggregate found in sedimentary beds in Brazil and the Central African Republic (which at one point were united) whose genesis remains a disputed mystery (high temperature creation from organic carbon within the earth, shock metamorphism from meteor impact, or radiation from natural fission?). Lead isotope analysis suggests formation 3 billion years ago. Carbonados are not associated with kimberlites.
Carbonatite35223130Carbonatite is a sub-class of alkaline rocks which is dominated by Carbonate Minerals, namely minerals with the CO3 carbonate ion. Normally when we hear about "carbonates" we think of sedimentary rocks such as limestone and dolomite which are host to skarn and replacement style mineralization containing metals such as gold, silver, zinc, lead or copper. In the case of a carbonatite we are dealing with an igneous intrusion which may be enriched in rare earths and other critical metals, but never contains diamonds in the manner of a kimberlite. Articles about carbonatites are far more important for rare earths than diamonds.
Chemistry191222Chemistry is a very generic term that encompasses all sorts of topics but the main one relevant to diamonds is what is called "inclusion chemistry", namely the chemical composition of minerals that form within a diamond at the same time as the diamond is forming in the mantle. Diamonds form within a precise range of pressure-temperature combinations. Other minerals such as garnets form not just within this range but beyond this range. A kimberlite magma entrains rocks encountered during its ascent and gradually disaggregates them so that individual crystals consisting of garnets, diamonds, and chromites end up distributed randomly within the kimberlitic magma. Inclusion chemistry is directed at determining whether or not rocks harvested during the magma's ascent are potential diamond bearing rocks. The trick is to identify those minerals which form exclusively within the PT range that supports diamond formation. If these are detected in a kimberlite sample or in till containing material a glacier scraped from an exposed kimberlite pipe or dyke, then the probability is high that the kimberlite source also contains diamonds. Articles about chemistry tend to focus on defining those relative compositions of the elements that make up the minerals that have been found inside diamonds. The term "diamond indicator minerals" refers to those minerals which have a formation range within the diamond stability field. Since all the minerals within a kimberlite are sourced from the mantle, but not all material is from the diamond stability field, it is possible to identify that subset, particularly in the case of garnets, which only shows up in diamondiferous kimberlites, as well as that set which only shows up in a kimberlite as compared to minerals formed under lower pressure conditions near the earth's surface such as almandine garnets. The broader term "kimberlite indicator minerals" is used to establish the "chemical" signature of a kimberlite and as an exploration tool.
Chromite8580Chromite is an iron chromium oxide of the spinel group which forms within the mantle in peridotite. It is relevant to diamonds as an indicator mineral because ascending magmas entrain chromite bearing material from the mantle.
Coesite31003Coesite is a form of silicon dioxide formed under ultra high pressure and temperature conditions (greater than 2.5 GPa and 700 degrees C which occurs at a depth of 70 km). It has been found in meteor impact craters and as eclogitic xenoliths in kimberlites. Eclogite evolves through the metamorphism created by subduction and continental collisions. Eclogitic diamonds are distinguished from peridotitic diamonds by including a greater range of carbon isotopes, including C13 which is never present in peridotitic diamonds whose carbon source was never exposed to sunlight whose radiation is critical to the C13 isotope. Peridotitic diamonds are Archean aged, whereas eclogitic diamonds can be younger. Articles about coesite are relevant to diamonds because coesite occurs in eclogitic xenoliths that are the source rocks for eclogitic diamonds.
Company Explorer - Other16897235The category Company Explorer - Other includes articles about companies engaged in diamond exploration which do not yet have a diamond deposit undergoing advanced feasibility demonstration work or already in production. The references do not include those which represent corporate news releases, only media reports about the company or, lss frequently, technical articles that discuss the project and to which Pat has also assigned the company name as a key word.
Company Producer - Alrosa18184415Alrosa is the Russian government controlled owner of most Russian diamond mines which went "public" in 2011. Alrosa is seeking to branch out beyond Russia.
Company Producer - BHP Billiton1634615BHP Billiton is a former major diamond producer which became involved with diamonds in 1990 when Hugo Dummett steered the mining giant into optioning the Ekati project in the Canadian Arctic generated by a junior called Dia Met Minerals Ltd headed by Chuck Fipke with Stu Blusson in a supporting role. BHP put the Ekati Mine into production and eventually absorbed Dia Met. BHP invested heavily in diamond exploration but, after failing to make another world class discovery, decided in 2012 to exit the diamond business by selling its diamond division to Dominion Diamonds, 40% partner with Rio Tinto in the nearby Diavik Mine.
Company Producer - De Beers48301091De Beers is the diamond mining and marketing giant founded by Cecil Rhodes in 1888 which consolidated South Africa's diamond mines to form a cartel that went on to brand diamonds as a major luxury good. De Beers has largely retreated from South Africa and now relies on its long term diamond supply through the Orapa and Jwaneng mines jointly owned with the Botswana government through Debswana. De Beers has put three Canadian diamond mines into production: Victor, Snap Lake and Gahcho Kue. It is also involved with marine diamond mining in South Africa and Namibia. De Beers' management of the rough diamond market through the Central Selling Organization (see Edward Jay Epstein for an account until the mid-eighties) began to erode in the eighties with Ashton's development of the Argyle Mine in Australia, in the nineties when the civil war in Angola unleashed a flood of aristanally mined diamonds, and at the turn of the century when Canada's Ekati and Diavik Mines came on stream with their own marketing strategies developed by BHP and Rio Tinto. The collapse of the Soviet Union also eventually enabled Russia to free itself from reliance on the CSO to market its diamond output to the western world. Today De Beers is just one of multiple rough diamond marketing channels though De Beers continues to spend heavily to cultivate consumer demand and stave off the threat from synthetic diamonds. The knowledge stranglehold De Beers once had on diamond exploration and evaluation theory dissolved with the explosion of global diamond exploration in the wake of the Canadian discoveries and the emergence of Russian technical expertise after the communist collapse.
Company Producer - Debswana - Government31993Debswana Diamond Company is the now 50:50 partnership De Beers and the Botswana government formed for the development of the world class Jwaneng and Orapa diamond mines as well as the smaller Letlhakane and Damtshaa mines. These are all media articles that deal with the Debswana owned diamond mines.
Company Producer - Dominion1944514Dominion Diamond Corp is Canada's largest independent diamond producer following its acquisition of the Ekati operation from BHP Billiton. Dominion has its origins as Aber Diamonds which optioned its holdings southeast of Ekati to Rio Tinto who discovered the Diavik cluster of high grade pipes, currently a 40:60 JV with Rio Tinto.
Company Producer - Endiama - Government43127Endiama is Angola's national diamond company which is the underlying owner of all diamond mining concessions. These are media articles that deal with Endiama's relations with its various partners and its diamond mining operations.
Company Producer - Firestone62110Firestone Diamond is an AIM-listed diamond producer with operations in Botswana (BK11) and Lesotho (Liqhobong).
Company Producer - Gem123580Gem Diamonds Ltd is the LSE-listed operator of the Letseng diamond mine in Lesotho which produces large, high value Type IIa diamonds from a very low grade pipe, as well as the newer Ghaghoo Mine in Botswana.
Company Producer - Lucapa32070Lucapa Diamond Company is the operator of the Lulo alluvial and bedrock concession in Angola which produces large, high value Type IIa diamonds from alluvial deposits and which explores for potential kimberlite pipes in the vicinity that may be the source of the alluvial diamonds. Lucapa also owns the Mothae pipe in Lesotho.
Company Producer - Lucara42590Lucara Diamond Corp is the operator of the Karowe Mine in Botswana, a producer of large, high value Type IIa diamonds.
Company Producer - Mbada - Government51320Mbada Diamond Company is the diamond arm of the Zimbabwe government owned Zimbabwe Consolidated Diamond Company (ZCDC) which ended up with control of the Marange diamond field in Zimbabwe.
Company Producer - Mountain Province51993Mountain Province Diamonds Inc is in a 49:51 joint venture with De Beers on the Gahcho Kue cluster of high grade diamond pipes in Canada's Northwest Territories. Gahcho Kue has a generally low value diamond population which appears to have a sub-population of very high value diamonds.
Company Producer - Namakwa71151Nawakma Diamonds is the operator of the Kao diamond mine in Lesotho, the largest kimberlite to go into production in Lesotho. Kao has very low grade and started production in 2012. Nawakma was an AIM listed company until its "privatization" delisting on Mar 22, 2013.
Company Producer - Namdeb - Government72524NAMDEB is a diamond mining company owned 50% by De Beers and 50% by the government of Namibia which was formed in 1994 to take ownership of the De Beers onshore and offshore diamond concessions on the coast of Namibia. Mining exploits alluvial deposits created by the Orange River whose tributaries drain the kimberlite fields near Kimberley in South Africa. The Orange River forms the border between Namibia and Sout Africa, with the coastal area from the Orange River's exit into the Atlantic Ocean about 70 km north to Luderitz designated as the SperrGebiet. This prohibited area was initially controlled by the Germans until the end of World War I when De Beers took control. In 2008 it was converted into a national park. The alluvial diamonds, which are predominantly gem quality because the long journey destroys lower quality diamonds, are also present to the south of the border on the South African coast. For an excellent overview of these onshore and offshore alluvial diamond deposits check out Marine Diamond Mining off the West Coast of southern Africa.
Company Producer - Other6710029Company Producer - Other includes articles, mainly media but some technical, for diamond producers that do not have their own major Key Word. An example would be Lukoil which ended up with 100% of the Grib pipe found in 1996 by a Canadian junior called Archangel Diamond Corp whose advanced work was bankrolled by De Beers until Archangel was mysteriously stripped of its just under 50% entitled share of this world class discovery. After the US Supreme Court dismissed Archangel's last legal challenge in November 2016 Lukoil sold the Grib Mine for $1.45 billion.
Company Producer - Petra105192Petra Diamonds Ltd is a London Stock Exchange listed (PDL) diamond producer which operates the Finsch, Cullinan, Koffiefontein and Kimberley mines in South Africa and the Williamson mine in Tanzania.
Company Producer - Rio Tinto2368627Rio Tinto, which ranks among the world's biggest mining companies, has a diamond division which has a 60% stake in the Diavik Mine in Canada's Northwest Territories and 100% of the Argle Mine in Australia. Until recently it was also trying to develop the Bondar pipe in India. In recent years Rio Tinto considered divesting itself of its diamond division as BHP Billiton had done, but seems to have decided to stay in the diamond business.
Company Producer - Rockwell42430Rockwell Diamonds Inc is a TSX and JSE listed diamond producer with alluvial diamond operations in South Africa.
Company Producer - Stellar31170Stellar Diamonds plc is an AIM-listed former diamond producer currently focused on developing mines in Guinea and Sierra Leone.
Company Producer - Stornoway71659Stornoway Diamond Corp is a TSX listed (SWY) diamond producer whose Renard diamond mine in Quebec, Canada began production in 2016.
Company Producer - Tans Hex92776Trans Hex Group is a JSE listed (TSX) diamond producer with alluvial diamond operations in South Africa and Angola.
Convection72318Convection is the manner by which heat generated inside the earth's core through radioactive decay causes hot rocks within the mantle (astheosphere) to rise while cooler rock sinks, creating a heat circulation that drives the plates which rest on the mantle (lithosphere). Convection is the engine that drivers plate tectonics and generates magmas which work their way to the surface. Convection is relevant to diamonds because it affects craton construction and eruption of kimberlites.
Core141342Core refers to the inner and outer cores of the earth comprised mainly of iron though also containing alloys involving oxygen, nickel and sulphur. The inner core is solid while the outer core is liquid. The outer core is the source of the earth's magnetic field.
Craton98100820Craton is that portion of the earth's lithosphere where crust and mantle represent the stable part of continents, usually in the interior of plates. A craton has thick roots which allow combinations of high pressure and low temperature that foster the formation of diamonds. Clifford's Rule is that commercial diamond deposits will only be found on cratons where ascending magmas sampled the diamond stability field. Articles with the keyword Shield are included under the major keyword Craton.
Crust272683Crust refers to the upper layer of the earth consisting of igneous, sedimentary and metamorphic rocks which divide into thinner oceanic crust and thicker continental crust. The crust is broken up into plates which float upon the mantle, whose motion is driven by convection cells which in turn give rise to plate subduction and collision, both of which yield to mountain building.
CSR441714CSR (Corporate Social Responsibility refers to a business model where a corporation engages in a form of enlightened self-interest whereby the profit motive is subordinated to serving the goals of multiple stakeholders of an environmental, social and political nature.
Deposits: pre 201615766514250The keyword Deposits indicates that the article discusses a particular diamond deposit.
Deposits: 2016 onwards15766514250The keyword Deposits indicates that the article discusses a particular diamond deposit.
Diamond - Color662030The keyword Diamond - Color indicates that the article discusses the color of a diamond which can range from colorless to almost every color such as pink, blue, green, and yellow as well as less desirable colors such as brown. These articles tend to deal with what causes a certain color to occur, and what the conditions might be for the formation of the color in a diamond.
Diamond - Conflict71102230Diamond - Conflict refers to the production of diamonds outside government regulation where the proceeds accrue to criminals or armed rebel groups. Such diamonds have become known as "blood diamonds" because of the brutal conditions inflicted on the artisanal miners and because the proceeds from the sale of smuggled diamonds bankrolls the violent agenda of rebel groups. These articles will include anything to do with the Kimberley Process which is a diamond industry initiative to isolate "illegal" diamond production from government regulated diamond production (it also is the defintiive source of annual country based diamond productiuon data in terms of both carat weight and value). The goal is to protect the marketability of natural diamonds by assuring consumers that the diamonds they purchase were produced through proper channels. Source certification and "fingerprinting" in order to guarantee the "clean" source of a diamond are covered by this keyword.
Diamond - Crystallography152583Diamond - Crystallography deals with the different crystal forms of diamond as well as the science of Crystallography which deals with how atoms are arranged in crystals.
Diamond - Cutting & Polishing685619Diamond - Cutting & Polishing articles are about the process of transforming a rough diamond recovered through alluvial or bedrock mining into a jewel that can be sold to consumers.
Diamond - Exploration7770715Diamond - Exploration articles are about the methods involved in finding and evaluating diamond deposits to determine if they can be commercially mined.
Diamond - General40158323Diamond - General articles have a broader focus on diamonds than technical articles which focus on a specific aspect of diamonds and the diamond industry, and thus are more accessible to the layperson. If you want to feel smart about diamonds, read these articles. Then to stop yourself from doing something stupid because you feel so smart, read the other types.
Diamond - Genesis31103616Diamond - Genesis articles deal with how diamonds are formed. A fascinating topic made absolutely mind-numbing by the experts.
Diamond - Grade6211Diamond - Grade articles deal with the problem of establishing the diamond content of a deposit in terms of carats per tonne (ct/t) or, as is often used in the industry to make low grade deposits less decimal-like, in terms of carats per hundred tonnes (cpht). This keyword is distinct from the problem of "grading" individual diamonds in terms of the 4 C's (carat, cut, clarity and color) for the purpose of valuing the diamond content of a deposit. These articles will focus on the statistical means for estimating the "macro" grade of a diamond deposit.
Diamond - Inclusions4974741Articles tagged with the keyword Diamond - Inclusions do not refer to things which diminish the quality of diamonds as defined by one of the 4C's called "clarity", as explained in diamond inclusions. These articles refer to the nature of the minerals that end up as inclusions inside a diamond. What may be the diamond buyer's curse is the scientist's bounty, for diamonds themselves beyond their carbon isotope distribution do not reveal much about the nature of the environment in which they formed. However, the chemistry of other minerals that managed to form at the same time as the diamond and ended up encased within the crystal structure of the diamond carry information about that inner part of the earth that no drill will ever penetrate. Because the pressure-temperature range under which diamonds form is known, the chemistry of inclusions are like messages in a bottle from deep within the earth. Diamond inclusions are also of great interest to diamond exploration because when it can be established that the chemical composition of certain inclusions forms only within the same pressure-temperature regime of diamonds, the presence of these minerals in a kimberlite implies the possibility of diamonds. It is only a coincidence that a garnet ended up inside a diamond whose formation is a much rarer event that that of the garnet. A chunk of rock from the diamond stability field entrained by a kimberlite magma will have many more "garnets" than diamonds. Whether one is collecting heavy minerals from till samples or extracting them from a piece of kimberlite, the chemistry of those minerals can reveal the probability of diamond content in the kimberlitic source rock. Needless to say, which "indicator minerals" are diagnostic of diamond potential is an ongoing debate.
Diamond - Industry Trends5400Diamond - Industry Trends are mainly media articles about trends within the diamond sector ranging from production to retail sales.
Diamond - Jewelry703933Articles tagged as Diamond - Jewelry deal with the diamond pipeline beyond cutting and polishing, and tend to be about liuxury goods retailers such as Tiffany and the marketing of diamonds as jewelry.
Diamond - Luminescence14761Diamond - Luminescence has nothing do with the ability of a diamond to reflect light, but rather with the ability to emit a "cold light" as a result of an energy stimulus. The Fluorescent Mineral Society provides explanations for the various forms of luminescence.
Diamond - Market189133026Articles tagged as Diamond - Market tend to be about rough diamond supply and demand trends, branding of diamonds, and various mechanisms for the sale of diamonds, including by producers.
Diamond - Morphology41116515Diamond - Morphology articles deal with the shape of a diamond as defined by the size and number of crystals in a diamond, and how the shape evolves.
Diamond - Processing373905Diamond - Processing articles deal with the recovery of diamonds from diamond bearing material, be it of an alluvial or bedrock nature. Unlike metal mining where the end product is delivered as either a powder or an ingot, the objective of diamond mining is to recover individual diamond crystals. Whereas a unit of copper or gold has the same value based exclusively on weight, a diamond's value is a function of weight and quality, with an exponentially higher value the bigger the diamond. A major diamond processing theme is thus the recovery of diamonds as efficiently as possible without crushing higher value large stones. A related topic that applies once the "liberation" problem has been solved is the extraction of diamonds from the rest of the material.
Diamond - Production2863310Diamond - Production articles deal with statistics about diamond production as opposed to the process of mining diamonds.
Diamond - Synthetics7868414Diamond - Synthetics articles deal with the above-ground production of diamonds from a carbon source using high temperature high pressure or chemical vapor deposition methods. The scientific articles deal with the mechanics of synthetic diamonds, whereas media articles deal with the market implications for natural diamonds versus synthetic diamonds.
Diamond - Treatment18351Diamond - Treatment articles deal with the ways natural diamonds can be treated to enhance their visual gemological quality through means such as irradiation, heating (annealing) or inclusion removal and replacement . Treated diamonds are controversial because the system for valuing natural rough diamonds is based on the concept of relative scarcity. By applying technology to transform a relatively abundant type of diamond such as yellow or brown diamonds into a more desirable and rarer form, the scarcity valuation basis is undermined. The diamond treatment topic is related to the production of synthetic diamonds.
Diamond - Types671401Diamond - Types is a variation of Diamond - Color which classifies diamonds according to the type of impurities rather than color. Type IIa diamonds which lack nitrogen as an impurity have become very topical because of their tendency to grow into very large sizes such as the Cullinan diamond and more recently Lucara's Lesedi La Rona diamond from the Karowe pipe in Botswana.
Diamond - Valuation443523Diamond - Valuation articles deal with the methods of modeling the average value of a deposit's diamond population and the 4C's system for assigning a value to a rough diamond based on its weight (carat), color (including colorless), clarity (refers not to colorlessness but rather the presence of visible impurities such as inclusions) and cut (properly crystal shape which determines how much waste is involving in cutting the rough diamond into a marketable gem).
Diatreme122191Diatreme refers to a volcanic eruption that results in the formation of a pipe like body. That, of course, is what a kimberlite pipe is, but this keyword refers to volcanic pipes unrelated to diamond bearing pipes such as a maar diatreme.
Discontinuity66810Discontinuity in the context of the diamond literature refers to the transition zones between the different parts of the earth from the crust to the inner core, but more specifically refers to the Moho Discontinuity between the crust and the mantle. A simpler way to describe it is to call it the thickness of the crust, which is relevant to diamonds because according to Clifford's Rule diamond form within thick cratons which allow high pressure at cooler temperatures that define the diamond stability field.
Dykes4728212Dykes refer to sheet like intrusions that never erupted. When they are near horizontal they are referred to as sills. Dykes and sills are relevant to diamonds when they consist of kimberlite, and although volumetrically small and likely requiring underground mining, have the advantage that their diamond grade has not been diluted by country rock infilling as happens when a kimberlite erupts and forms a pipe.
Eclogite3472127Eclogite is a mafic metamorphic rock formed at pressures higher than found in the earth's crust and likely created when basaltic oceanic crust is subducted so that it underplates a craton. It is a primary source rock for diamonds that is distinct from the other main source rocks, harzburgite and lherzolite. "Ecologitic" garnets formed within eclogite have chemistry distinct from that of "pyrope" garnets formed within harzburgite and lherzolite (the G9-G10 series). Xenoliths of ecologite found within kimberlite have demonstrated a much higher diamond grade than xenoliths of harzburgite or lherzolite. Diamonds from harzburgitic or lherzolitic source rocks have an Archean formation age and a narrow carbon isotope range that excludes C13 which requires exposure to sunlight to form. Because ecologite is formed from subducted oceanic crust it will have derived some of its carbon from ocean floor sediments that include limestones, whereas the diamonds in harzgburgite would have had to scavenge primeval carbon from the peridotite host. "Ecologic" diamonds can be much younger than "peridotitic" diamonds, and, may be formed deeper because the crustal source rock was subducted underneath a craton. Because a kimberlitic magma starts its ascent even deeper, it is possible for the magma to entrain both ecologite and harzburgite/lhzerloite during its ascent. Kimberlites dominated by eclogitic chemistry tend to be found at craton margins which reflects the unlikelihood that subducting crust would end up underneath the thickest part of the craton which preserved peridotitic diamonds formed during the Archean period.
Economics55238722Articles tagged with the key word Economics are typically media rather than scientific journal articles and cover a broad range of topics such as the economics of the three main stages of the diamond pipeline (mining, cutting & polishing, retail sales), country production data, taxation and other government policies relevant to diamonds, the diamond industry in general, and the diamond market itself. Many of the articles could be tagged with a more specific key word and some are unusual or wide-ranging enough to defy key word tagging. The "economics" page is thus a good place to look for very interesting articles about the diamond sector.
Emplacement17544Emplacement is a subset of the key word "volcanism" and flags scientific articles dealing with the ascent and eruption of kimberlite pipes, the primary source of bedrock hosted diamonds. These articles tend to focus more on the physical model as to how a kimberlite gets "emplaced" than the classification of the various parts of an emplaced kimberlite.
Environmental152445Environmental tagged articles deal with a wide range of topics that focus on both environmental and social license issues. This topic overlaps with other key words that are more specific. The relationship to diamonds involves the question of wther or not, and under what terms, a diamond deposit can be put into production.
Foidite2200Foidite, which also goes by the name Foidolite when referring to the rock itself, is a coarse grained igneous intrusion with more than 60% feldpathoid minerals that does not seem to have much to do with diamonds other than being a rare volcanic resembling a kimberlite.
Garnet262951A Garnet is a semi-precious silicate mineral used for jewelry and as an abrasive. Almandine garnets are the common variety formed within metamorphic rocks such as schist, but the garnets relevant to diamonds are the pryope garnets which form in ultramafic rocks under high pressure conditions within the mantle such as peridotite (harzburgite and lherzolite) and eclogite. Statistical studies have demonstrated that certain relative composition ranges of chromium and calcium within pyrope garnets correlate with temperature-pressure conditions that foster diamond formation. This has allowed pyrope garnets derived from kimberlite pipes to serve as diamond indicator minerals.
Gemstones312370Gemstones are mineral crystals which can be cut and polished for the jewelry trade. These articles tend to be scientific and about gemstones other than diamonds.
Geochemistry123227575Geochemistry can be about the relative composition of elements and their isotopes within rocks, but also about the mechanisms that drive the movement of matter within the earth.
Geochronology882446111Geochronology is the science of determining the age of rocks, fossils and sediments through the use of radioactive isotopes and paleomagnetism. These are exclusively scientific articles that deal with the age of the earth, and, more relevant to diamonds, the emplacement age of kimberlites.
Geodynamics264306Geodynamics is about the processes that move material within the earth, such as convection cells and plate tectonics, as well as mountain chain building, described in geophysical terms, as opposed to geochemistry which describes these mechanisms in terms of chemsitry. The closest these scientific articles come to being relevant to diamonds is when they discuss cratons, the thick stable chunks of continental crust where diamonds form.
Geology21112317Geology is such an enormously broad topic that it is surprising that a fairly modest number of mainly scientific articles have been tagged with that key word. These articles tend to be about the makeup of specific kimberlites or regions.
Geomorphology1262618Geomorphology is the study of the forms the earth manifests at the surface, which in layman terms is about landscapes and the erosional forces that shaped them. One of those forces very relevant to diamonds is the glacier, or ice sheet, whose passage over erupted kimberlties scrapes out material and drags it up to several hundred kilometres from the source. This has two effects. One is the excavation of the kimberlite if it is softer than the country rock into which it was emplaced, and the other is the resulting indictor mineral train in the direction of the glacier flow which becomes an exploration path back to the kimberlite source.
Geophysics17119419In the resource sector the term Geophysics is treated as short-hand for the various methods used to measure physical aspects of the earth, collected under the umbrella term "geophysical surveys". But as the Wikipedia entry reveals, "geophysics" is a scientific term that refers to all the physical processes and nature of the earth as well as the methods used to measure them. Articles tagged with the key word "geophysics" are always of a scientific or technical nature. Sometimes they are about the measurement technology itself, but most of the time they are about what geophysical methods have revealed about the earth ranging from the large scale structure of the earth's mantle to the small scale structure of a kimberlite pipe. Some of the articles are about the process that resulted in whatever physical state exists at different scales, which seems hard to imagine as possible. Yet one of the most fascinating goals of academic geology is to conjure a transformational history of the earth. Many other obscure key words such as "geochronology", "rheology" and "tomography" show up in articles. They are relevant to diamonds when they describe the conditions conducive to diamond formation, and when they describe the pipe or dyke like intrusions that can host diamonds.
Geophysics - Gravity1623811Geophysics - Gravity articles are about the use of relative density of the earth's sub-surface to describe the geological variation of rocks. Gravity geophysics can be relevant to diamond exploration when it highlights an intrusion by showing it to be more or less dense than the country rock. These articles tend to be about how gravity surveys work or about how known pipe can be revealed through gravity surveys.
Geophysics - Hyperspectral8131Articles tagged Geophysics - Hyperspectral are about "hyperspectral imaging", the collection of images of a surface that includes the entire reflected electro-magnetic spectrum of wave-lengths, not just the colors a human would see through an eye in the sky otherwise known as a satellite, and the processing algorithms that extract knowledge from the resulting grid of pixels. The idea is that different molecules reflect different wavelengths, which molecules can be organic as in vegetation or inorganic as in the minerals that make up rocks. Hyperspectral data can be collected at different scales, such as satellites that orbit the earth, airplanes that collect much higher resolution data by flying over target areas, and even at the hand-held level where a kimberlite core or an indicator mineral sample can be scanned. It is a subset of "remote sensing". What distinguishes hyperspectral surveys from most other geophysical surveys is that they are passive in the sense that they simply collect what natural radiation is reflected by surfaces (or not when it is in fact absorbed, creating distinct "holes" that are themselves valuable information). Other geophysical methods such as seismic or magnetic surveys involve bombarding the earth's surface with "radiation" of some form and measuring the reflection pattern. The interpretation of hyperspectral data requires massive computational power and a database of "patterns" that correlate with known physical things such as the reflection characteristics of certain minerals that are formed when rock undergoes alteration due to a hydrothermal system. But even when a definitive interpretative template is not available, the analysis can reveal lateral variation which piques curiosity as to what might be responsible, and leads to new pattern mapping definitions. The ability to create time series snapshots of the earth's surface also makes it possible to observe changes over human time scales, and while these are not interesting to geologists except when they involve retreating glaciers that might reveal never before seen outcropping mineralization, they are of great interest to environmentalists and anybody else impacted by a changing landscape. Articles about hyperspectral imaging can be relevant to diamond when it involves recognizing erupted kimberlites, but they are more interesting when they are about methods which allow rapid quantified identification of diamond indicator minerals in either a till sample or a crushed kimberlite sample.
Geophysics - Magnetic1722812Articles tagged as Geophysics - Magnetics tend to deal with measuring the magnetic variations within the earth vertically and horizontally (usually through aeromagnetic surveys), which involves two entirely different dimensions, one being the relative magnetic intensity of rocks, and the other being the magnetic polarity of the rocks. The earth has a history of switching the north-south polarity of its magnetic field, which geologists first figured out when trying to understand the magnetic zebra pattern of oceanic crust. It turns out that in a magma "crystals" point in every possible direction, but when they chill they line up according to the prevailing polarity of the magnetic field. One thus has to be cautious about magnetic "lows" and "highs" due to reversed polarities of the rock's magnetic minerals, and due to the relative abundance of magnetic minerals in different adjacent rock types. But these articles can also be about what magnetic surveys have revealed about the nature of the earth not just as it is configured now, but also as it evolved. In fact, some articles are about the rocks reveal about the history of the earth's magnetic field which is drive by the inner core. Magnetic geophysical surveys are not relevant to diamonds themselves, but they are very important to exploration for mantle derived intrusions such as lamproites and kimberlites which intruded the upper crust rather quickly and chilled very quickly.
Geophysics - Magnetotellurics10541Articles tagged Geophysics - Magnetotelluricsinvolve magnetotellurics, a geophysical method that involves measuring the earth's sub-surface conductivity by measuring magnetic field variation. Whatever this means, I am not there yet. I do know it has nothing to do with Magneto of the X-Men, about whom I think every time I hear this word.
Geophysics - Seismic521900118While "gravity", "magnetic" and "induced polarity" geophysical surveys focus on lateral differences in the composition of the earth at different scales, the "seismic surveys" referred to by the key word Geophysics - Seismic attempt to describe differences in the earth's composition in the vertical dimension. These articles are all of a scientific nature and have little to do with diamonds other than describing the inner structure of the earth and highlighting those regions conducive to diamond formation and kimberlite eruptions.
Geotectonics2980This is a duplication of "tectonics" and will be converted into a sub key word assigned to the key word "tectonics".
Geothermobarometry3589644Geothermobarometry is the science of measuring the pressure and temperature history of metamorphic and igneous rocks through examination of the chemical composition of individual minerals and the assemblages of different minerals. Geobarometry focuses on establishing the pressure conditions associated with mineral formation whereas Geothermometry focuses on the temperature conditions. The SDLRC also uses Thermobarometry and Thermometry as key words. This topic is relevant to diamonds because it enables the establishment of unique correlations between diamonds and other minerals based on pressure-temperature regimes.
Glaciology151300Glaciology is a broad inter-disciplinary term that takes the emergence and disappearance of glaciers, namely ice on the surface of the earth, as its focus. Articles dealing with the rise and fall if ice sheets as well as climatology issues are tagged by this keyword. The history of the earth's climate, such as the "snowball earth" phenomenon, is not relevant to diamonds, but the effect of glaciers, better described as "ice sheets", on kimberlite pipes or dykes exposed at the surface, is veyr relevant to diamond exploration. When a glacier (ice sheet) flows over the earth's surface, it picks up loose material such as boulders, which become the equivalent of garnets stuck on a piece of paper, namely sandpaper. As the ice sheet flow, its "sandpaper" base scrapes the country rock. When it encounters relatively softer material, such as what kimberlites typically are when erupted into an Archean terrain, the ice sheet preferentially gouges out the kimberlite pipe. The gouged up kimberlite material becomes part of the ice sheet's "sandpaper" base, and gets dragged along by the ice sheet. When climate change stalls the buildup of ice, the ice sheet stops flowing. As it melts, it drops the components of its "sandpaper" base. The result is a "train" of "kimberlite indicator minerals" emanating from the exposed kimberlitic source. An exploration strategy of grid based regional till sampling whereby the heavy minerals are isolated and analyzed as to mineral type and composition can reveal a train of indicator minerals that terminates at or near the source. While some of the glaciology articles deal only with the earth's climate history, others deal with the behavior of glaciers. This is relevant to diamond exploration because glacial flow direction can be complex over time and undermine the exploration model of a linear train of indicator minerals from the source.
Harzburgite3610Harzburgite is a form of peridotite comprised mainly of olivine and pyroxene.
History53126918When Pat Sheahan tags an article with the single keyword History whether in the technical or media literature odds are good that it is reasonably accessible to non-diamond-industry readers. If she included additional terms the reference will end up in the relevant major keyword report. When Pat publishes her monthly list of new references, it is always worthwhile to check out the new yellow highlighted articles in the History report. Scientific articles will have an abstract and a ink to a prettier version of the abstract and sometimes the full article, though usually just to the means for purchasing the full article. Media articles link to the usually unrestricted online content. The History section is Pat Sheahan's ultimate goodie bag.
Hotspots72607Hotspots may be mobile and hot, but they have nothing to do with the mobile hotspots craved by millenials. A hotspot is an area of volcanic activity caused by a near surface magma which may be due to a local melt or a plume rising from the mantle. The former is not relevant to diamonds, but the latter is because its lateral passage (wandering) through the mantle will disrupt the diamond stability field where diamonds may have been forming since Archean time. The "wandering" is the effect of plate tectonics moving crustal plates while the mantle plume remains stable. The other type of volcanic hotspot is caused by subduction or rifting.
Ignore18403The Ignore report features articles with a "keyword" intended to elaborate on a prior keyword such as "not specific to diamonds". Pat Sheahan uses a comma to separate keywords, which we have used to computationally extract individual key words or phrases from the 50,000 plus references she has compiled since 2004, all of which are available within the Diamond Resource Center. When John Kaiser cannot figure out what major keyword a secondary keyword is related to, he leaves it classified as "Unknown". But when it seems to him it was just an elaboration of a prior keyword, he tags it as "Ignore". This report enables Pat to check up on John's decisions and let him know if a major keyword match is appropriate. So please ignore this link, it is not meant to be useful to anybody but Pat and John.
Ilmenite4410Ilmenite is an iron-titanium oxide mineral that is the primary ore from which titanium dioxide is derived. Ilmenite can occur within kimberlite whose ascending magma may entrain ilmenite whose occurrence is not restricted to the diamond stability field. Ilmenite is treated as a "kimberlite indicator mineral" as opposed to a "diamond indicator mineral" because its recovery in glaciated terrains that lack a natural abundance of ilmenite bearing rocks can point to a kimberlite source. This also applies in non-glaciated setting such as the Kalahari Desert where termite mounds are investigated for anomalous quantities of kimberlite indicator minerals. The presence of ilmenite may signal a nearby kimberlite but it conveys no information about diamond potential.
Impact Crater15811An Impact Crater is the depression created in the earth's crust when struck by an asteroid or meteor. The moon is full of such completely preserved impact craters, but on the earth they are only preserved when fairly recent or within a stable craton. Scientific articles about impact craters are relevant to diamonds because major impacts can affect melting behavior within the earth's mantle which leads to magmatism which in turn can spawn kimberlite emplacement. Extraterrestrial impacts also create high pressure and high temperature conditions that support diamond formation, though so-called impact diamonds tend to be small and have a hexagonal crystal structure similar to graphite.
Kamafugite4350A kamafugite is an igneous intrusion that has a fair number of scientific references but is so obscure it does not even have a Wikipedia entry. Perhaps Roger Mitchell will be so kind as to pen a brief description and why it is is relevant to diamonds, ideally with a link to an online resource with greater detail.
Kimberlite115222921Kimberlite is an igneous intrusion whose dominant content has a magmatic source at a depth of 150-400 km within the earth's mantle. Kimberlitic intrusions are unusual in that they appear to originate through discrete melting within the mantle whose resulting magma ascends through the mantle, entraining "xenoliths" of mantle material along the way, generally but not always entirely disaggregating the entrained material, exploiting zones of crustal weakness, and achieving emplacement by cooling within sub-vertical faults to form dykes or stratigraphic horizons to form sills, or gaining velocity and erupting explosively to form pipes with a classical morphology of a crater, diatreme, and root zone. References tagged with the keyword "kimberlite" are about kimberlites in general or specific kimberlites that have not become mines or scheduled for development. Commercial or potentially commercial kimberlites will usually have a key word in the format "Deposit - Venetia" or just "Venetia" which results in their articles showing up in the Deposits report.
Lamproite196946A Lamproite is an ultrapotassic mantle derived intrusion which, unlike a kmberlite whose emplacement setting is limited to cratons, can show up anywhere. But because a lamproite originates from depths as much as 150 km, it is capable of sampling diamond source rocks within the diamond stability field during its ascent. The Argyle Pipe in Australia is the biggest and richest example of a diamondiferous lamproite. Because lamproites tend to be associated with craton margins or mantle plumes, neither of which setting is conducive for diamond formation or preservation, articles about lamproites tend to be very "scientific".
Lamprophyre162363A Lamprophyre is a volumetrically small ultrapotassic intrusion similar to a lamproite but with no record of being diamond bearing, possibly because they have a fairly shallow origin related to granitic intrusions. Lamprophyres have been spatially associated with orogenic lode gold deposits though no genetic relationship has been established.
Legal32281748There probably is no key word that triggers a greater dread of tedium than legal other than those scientific sounding ones with five or more syllables, but to avoid "legal" tagged articles, which are overwhelmingly media articles, is to fail to appreciate that Pat uses this word as a euphemism for controversial. Some of the articles deal with diamond theft escapades, which are intrinsically entertaining, but most deal with conflicts and dilemmas involving industry practices, government policies, and reporting regulations. If you want to be on top of what is getting people in the diamond industry worked up, and do not care about the synthetics versus natural debate, and know that articles involving the Kimberley Process and conflict diamonds have their own special key word Diamonds - Conflict, always check this section when a new monthly issue of the Sheahan Diamond Literature Service is published.
Lherzolite51371Lherzolite is an ultramafic igneous rock formed in the earth's upper mantle to a depth of 300 km. It is the most dominant form of peridotite. G9 pyrope garnets are associated with lherzolite whereas G10 garnets are associated with harzburgite. During the eighties the theory emerged that G10 garnets were diagnostic of diamond potential, with the G10/G9 line pioneered by John Gurney as separating diamondiferous from non-diamondiferous kimberlites. The G10/G9 line was based on the relative composition of Cr2O3 (chromium) and CaO (calcium) within a pyrope garnet. The rule of thumb was that the higher the chromium content and the lower the calcium, the better the diamond potential. Later work by Gurney and Herman Grutter refined this model so that G10 and G9 garnets above a minimum Cr2O3 level were deemed diagnostic. The rethink was partly driven by the discovery of lherzolitic xenoliths (G9) that were chock full of diamonds.
Lithosphere41697Lithosphere is the crust and the near solid uppermost part of the mantle.
Magmatism63103543Articles tagged with the key word magmatism tend to deal with the behavior of magmas within the earth's crust either as mountain building batholiths or volcanic eruptions, which distinguishes them from articles tagged as melting which deal with magma formation. None of these predominantly scientific articles have anything to do with diamonds unless they deal with diamond bearing kimberlitic or lamproitic magmas.
Mantle79102445Mantle refers to the portion of the earth's interior between the crust and the outer core which is in a solid to plastic state.
Massif25701A Massif is a portion of the crust that has been demarcated by faults and displaced from its source without changing its internal structure.
Melting4258717Volcanoes are vivid in the public's imagination, but almost absent is what takes place within the earth's mantle, the semi-solid layer between the molten outer core and the solid lithosphere (crust) whose convection cells drive plate tectonics. The key word melting tags articles which deal with the development of magmas within the mantle that manage to ascend into the lithosphere and become either igneous intrusions that chill before ever reaching the earth's surface or breach the surface as a volcanic eruption or basaltic flow. There is a wide range of magmatic intrusions which penetrate the crust, of which the most important for diamonds are kimberlites and lamproites, none of whose eruption at surface has ever been recorded as witnessed by human beings. Articles tagged as "melting" deal with the conditions that allow part of the mantle to melt into a magma with a distinct chemical composition that works its way through the mantle into the crust and ultimately in some cases onto the surface. This is a fascinating topic but written in very technical terms which means that the articles are universally of a scientific nature.
Metamorphism122919Metamorphism refers to gradual change of a rock's chemistry or texture while remaining solid, mainly through a combination of pressure and heat over long time periods. These articles are scientific and deal with metamorphic rocks such as massifs which can contain diamonds, though not of commercial size and quality and the processes by which diamond source rocks such as eclogite and harzburgite form.
Metasomatism2038913Metasomatism is the chemical alteration of rock through fluid flow, mainly of a hydrothermal nature, which distinguishes it from metamorphism which changes the minerals without altering the chemical composition. Fluid flow replaces existing minerals with others derived from elements dissolved in the fluids, which in turn makes it a major metal deposit forming mechanism. In this sense metasomatism is not relevant to diamonds, but it is also applied to transformations of the composition of the mantle through the fluid flows created by melting, which provides the magma source for kimberlites and also affects the craton keels where diamonds form in the diamond stability field. These articles are all of a scientific nature and extremely technical.
Meteorites192032Articles tagged as are usually of a scientific nature and deal with the tiny diamonds and other unusual carbon based crystals formed through the high pressures created by a meteor impact.
Microdiamonds141435Microdiamonds are diamonds that fall through a 0.85 mm sieve with anything larger described as a macrodiamond. The prevailing theory is that the formation of a diamond population follows a lognormal size frequency distribution which means that for any unit of rock there are going to be a lot more very small diamonds than big diamonds. But only "macrodiamonds" have commercial value in the jewelry sector, which is why historically the evaluation of a kimberlite for diamond grade required testing of large samples through dense media separation that recovered only stones bigger than 0.85 mm. Prior to the nineties the standard exploration strategy upon discovering a kimberlite was to analyze the chemistry of the kimberlite's minerals and compare it to a database De Beers developed during the 20th century by extracting inclusions from diamonds. Under this approach De Beers cataloged the chemistry of all the minerals found in a kimberlite as well as the diamond content established through bulk sampling. Over time it became apparent that garnets with certain chemical composition ranges recovered as diamond inclusions tended not to exist in barren kimberlites. The theory emerged that such minerals, of which pyrope garnets of the G10/G9 variety were the most diagnostic group, grew only in the same pressure-temperature regime in which diamonds formed. Because these minerals were far more abundant than diamonds it became cost effective to assess the diamond indicator mineral chemistry of a kimberlite before incurring the expense of testing for actual diamond content. The wisdom of this approach was called into question after Ashton discovered the Argyle pipe in Australia which had an unusually high macro grade of about 500 cpht. The problem it posed was that it was a lamproite whose minerals had a chemistry very different from that of the kimberlites derived from the peridotitic kimberlites that dominated the De Beers database. The Orapa pipe in Botswana, a true kimberlite but with a diamond content vastly superior to that of Argyle, was also problematic because it lacked G10/G9 pyrope chemistry. Exploration groups such as Ashton developed a strategy where once a kimberlite was found it was subjected to caustic fusion or acid dissolution for the recovery of any size of diamond. The more diamonds and the bigger the better the potential for a macro grade. This allowed exploration companies to use a sample smaller than 100 kg recovered through core drilling to assess the diamond potential of a new kimberlite. During the nineties when BHP and Dia Met discovered the Ekati kimberlite field in Canada's Arctic a reporting standard somewhat arbitrarily emerged where all of the diamonds were measured in their longest dimension and classified as either 0.5 mm or bigger, or smaller than 0.5 mm: the bigger ones were called "macros" and the smaller ones "micros". From this emerged the notion that the more macros per kg of sample, the better the macro grade potential. More dubious was the idea that the ratio of macro to micro counts was indicative of macro grade potential. This approach benefited from simply not recovering or counting the smallest diamonds. The 0.5 mm in the longest dimension distinction attracted criticism after several bulk samples in 1994 from supposedly promising pipes delivered disappointing low grades. Ironically, the infamous Tli Kwi Cho Bust was not the result of misinterpreting the grade potential of the DO27 pipe, but rather by a failure of the operator, Rio Tinto, to delineate the geology of the pipe and design an underground bulk sample to recover a representative sample of the different kimberlite units. The first scientist to push the idea that macro grade could be predicted from microdiamond size frequencies was Luc Rombouts, a theme further developed by John Chapman and Grant Boxer who worked with the Argyle data sets. Ironically, Ashton Canada only published micro diamonds according to the discredited 0.5 mm longest dimension classification. A multi-sieve based reporting system for micro diamonds first appeared when De Beers started reporting such results for the Gahcho Kue pipes optioned from Mountain Province. The driving force behind this approach was Johann Ferreira whose sieve system was modified through the publication of the CIM Diamond Exploration Reporting Guideline. Since then all "microdiamond" results have been reported according to a root two progression sieve system. This has enabled investors to plot on a log 10 scale the normalized counts per sieve size which should result in a straight line. The diamond grade is the area under this curve from the cut-off sieve size onwards. The shallower the slope of the microdiamond size frequency distribution curve, the "coarser" the distribution and thus the better the potential for large diamonds which is not necessarily related to the overall macro grade. Articles tagged with the key word "microdiamonds" tend to be about the method of using microdiamonds to predict grade and the associated pitfalls, which is relevant to diamond exploration. However, there is some controversy about the origin of microdiamonds under conditions not conducive to the formation of commercial size "macro" diamonds such as high pressure conditions created through meteor impacts or in subduction zones. Some articles thus deal with unusual rocks with high micro diamond counts such as the Dachine Massif and the Wawa conglomerates.
Mine - Argyle62504Articles tagged Mine - Argyle are media articles about the Argyle diamond pipe found in 1979 in Australia by Ashton Mining and now owned by Rio Tinto. Argyle was unusual in that it is a lamproite in a craton margin setting that was very large with a high grade of 500 cpht. The diamonds do not have a coarse size distribution with the result that the mining method does not attempt to recover stones bigger than 2 carats. Argyle diamonds have a brownish to yellow color which De Beers refused to market, forcing Argyle in association with Rio Tinto's Australian subsidiary CRA Associates to develop their own marketing system for diamonds branded as "cognac" and "champagne".
Mine - Diavik722613Articles tagged Mine - Diavik are media articles about the Diavik diamond project next to the Ekati project discovered in 1994 and operated 60% by Rio Tinto and 40% by Dominion Diamonds.
Mine - Ekati4925Articles tagged Mine - Ekati are media articles about the Ekati diamond field discovered in 1991 in the Northwest Territories of Canada by Dia Met Minerals, developed by BHP Billiton and now operated by Dominion Diamonds.
Mine - Marange72950Mine - Marange refers to the Marange diamond field in eastern Zimbabwe that is now controlled by the government agency Zimbabwe Mining Deevlopment Corporation (ZMDC). The Marange is a paleoplacer deposit of alluvial diamonds discovered by De Beers in 2000 which was subsequently over-run by artisanal workers after De Beers dropped out in 2006. The diamond are hosted in 2-3 metre thick conglomerate beds within the Umkundo Basin. Although there are kimberlites in the vicinity they are not the source of the diamond because they are younger. The source is unknown and some of the diamonds exhibit roundedness indicative of transport over long distances. Only 10% of the stones are gem quality. A Summer Symposium 2012 Field Trip article produced by the Geological Society of Zimbabwe provides a good geological overview. Because of illegal mining and associated corruption the Marange diamonds have been a controversial topic in human rights and environmental terms. The uncontrolled output also put pressure on diamond prices from 2008 until 2014 when the easy supply of alluvial diamonds ran out. These are all media articles.
Mine - Other8360The key word MIne - Other is applied to all articles that are about a specific diamond mine which does not have its own key word. These are all media articles.
Mineral Chemistry2659518If you thought articles tagged as Mineralogy were a black hole best avoided, then you know that you must never click on the section for scientific articles tagged as Mineral Chemistry. Many of these articles were written by hyper-specialized academics, some of whom are evil enough to embed the word "diamond" in the title in a desperate ploy to get at least one non-AI entity to read it. But most of the writers are honest and do give us warning titles such as "Crystallographic preferred orientation of wadsleyite and ringwoodite: effects of phase transformation and water on seismic anisotropy in the mantle transition zone".
Mineralogy38121722One look at the Wikipedia entry for Mineralogy tells you that these scientific articles with highly technical titles are exclusively for the diamond sector's scientists. If you think the title "Distribution and processing of highly siderophile elements in cratonic mantle lithosphere" has something to do with pornography, do not go there. But if you do, you will find in this article's case that the abstract is almost a paper in its own right, and if you do not reluctantly feel a tug to tackle it and the underlying article, then you fall into that category of people "who do not know what they don't know".
Mining123108712Articles tagged as Miningcover a wide range of mining related topics that include mining methods both in general and as applied to particular mining operations, as well as problems associated with mining. About two thirds of the articles are media articles and the remainder are scientific.
Miscellaneous58103213References classified as "Miscellaneous" involve keywords that are interesting in their own right but either are not used frequently enough to justify their own web page or have not been assigned to a Major Keyword.
Moissanite3570Moissanite is the name given to natural silicon carbide which has been found in meteor impact craters and some kimberlites and lamproites. It has also been found as inclusions within diamonds. Because natural silicon carbide is very rare, all applications use synthetic silicon carbide. Because of its optical properties and hardness just below diamond synthetic moissanite has been marketed as an alternative to diamond.
Nitrogen7611Articles tagged as nitrogen related tend to be very scientific with little relevance to diamonds except when they deal with nitrogen as a diamond impurity which causes a yellow color that is a bad thing unless the intensity is such that the yellow color can be classified as "fancy" rather than being reminiscent of unpleasant bodily secretions such as urine, gall stones and kidney stones.
Olivine15850Olivine is a magnesium iron silicate that is a primary constituent of peridotite, the dominant material in the mantle. oOlivines have a greenish color linked to the presence of nickel which inserts itself into the olivine mineral's crystal lattice which can account for a nickel grade as high as 0.25% that has zero economic value because of the very high energy cost of liberating the nickel from its crystal prison. Olivines are relevant to diamonds because they occur in kimberlites.
Orogeny212238Orogeny refers to what happens when tectonic plates encounter each other, something which lay people might characterize as transformational ecstasy but which geologists less imaginatively characterize as "deformation". If the encounter involves a denser oceanic plate and a lighter continental crust, the result will be subduction as the denser oceanic plate slides beneath the lighter continental crust. Subduction releases energy in the form of heat which causes melting that drives magmatism which in turn builds mountain chains through igneous intrusions or volcanic extrusions. When blocks of continental crust with similar density collide, the result can be mountain building in the style of the Rockies, the Alps or the Himalayas which force existing crust skywards. Alternatively the energy generated through the collision can result in deformation, the compression of crustal rocks so that they undergo folding and metamorphism on a regional scale. Because this activity takes place close to the earth's surface there is not much relevance to diamonds, but it is of great relevance to deposit formation both because of structural preparation created by deformation and because of large scale "orogenic" fluid mobilization which harvests metals from crustal rocks and drops them out under the right geochemical and structural conditions.
Paleomagnetism61692Paleomagnetism is the study of the history of the earth's magnetic field as recorded in the earth's rocks. The polarity of the earth's magnetic field periodically reverses, which has been observed in the zebra stripe alternation of oceanic crust from magnetic high to low. As magma upwells within ocean spreading centers the magnetite crystals initially have a random orientation, but as the magma gradually cools the magnetite crystals orient themselves in a north-south direction. Ocean floor formed during a period when the magnetic field has a north-south polarity will exhibit that magnetic orientation; when the poles reversed the subsequently created ocean floor will have the opposite polarity, hence the zebra stripe observed by surveys that measure magnetism. Paleomagnetism is relevant to diamonds because an erupting kimberlite is in a molten state, but as the kimberlitic magma cools the magnetite crystals will orientate themselves according to the current polarity of the earth's magnetic field. How the magnetite within the kimberlite body is oriented relative to the magnetite in the country rock will determine the degree that a kimberlite will stand out as a magnetic anomaly.
Peridotite283567Peridotite is an ultramafic igneous rock (less than 45% silica) consisting mostly of olivine and pyroxene that compromises most of the earth's upper mantle (to a depth of 400 km). When the oliovine drops below 40% the rock is classified as a pyroxenite. Oceanic plate, about 100 km thick, consists of peridotite except for the upper 6 km or so. Oceanic plate gets subducted back into the mantle, but sometimes it rides over the continental crust (obduction) to form "massifs" that seem out of place. Peridotite classifies into dunite, wehrlite, harzurgite and lherzolite of which lherzolite is dominant. Harzburgite is the source rock most associated with diamond formation, though lherzolite, because of its broad range within the mantle, can also host diamonds. Kimberlites will contain xenoliths of the different types of peridotite.
Perovskite71663Perovskite is a calcium titanium oxide mineral formed in the mantle. It is relevant to diamonds because it can show up in kimberlites. These articles require specialized chemical knowledge to be comprehensible.
Petrology42171530Petrology is the study of the origin, composition, distribution and structure of rocks, whereas petrography is the detailed description of the composition and texture of the minerals within a rock. Articles tagged with the keyword petrology can thus be about nearly any topic, whereas petrography articles will tend to be either about classifying the physical aspects of an emplaced kimberlite, or applying a petrographic classification system to a specific kimberlite.
Picrites71603Picrite is a form of basalt rich in magnesium and olivine such as that which formed the Hawaiian Islands. Picrite is not relevant to diamonds.
Plate Tectonics251861Plate Tectonics is the most important scientific theory to emerge in the field of geology which is apparent in the detailed Wikipedia discussion. The theory has its roots in the observation of Alfred Wegener in 1912 that the continents appear to fit together, leading to the notion of "continental drift". But what puzzled everybody was what mechanism drove the movements of this earthly jigsaw puzzle. The emergence of geophysical surveys after World War II helped illuminate the seafloor so that the lithosphere came to be understood as a mobile assembly of "plates". But geophysics also illuminated the earth's innards, which led to the theory of plate tectonics in the mid sixties, namely that the semi-solid mantle between the liquid outer core and the solid crust sustains convection cells which drive the lateral movement of the lithospheric plates, causing magmatic upwellings at seafloor spreading centers as well as within the subduction zones where denser oceanic plates slid under lighter continental crust, and orogenies where crustal plates collide with each other to drive mountain building uplift as well as metamorphism. Articles tagged as "plate tectonics" tend to be of a scientific nature and deal with the movement of plates and the mechanisms driving this movement. The topic is relevant to diamonds because diamonds are formed in the mantle, but it is the nature of the crust and the phenomenon of discrete magmatism which results in diamond being available for discovery at the earth's surface where pressure and temperature conditions are such that it is impossible for diamonds to form. Diamonds are relevant to plate tectonics because they are "messages in a bottle" from inside the earth whose commercial value enables scientific research into the nature and history of the earth.
Plume2650811The key word Plume refers to a "hotspot" at the earth's surface which is not related to the volcanic activity associated with subduction zones where oceanic plate descends beneath continental crust, but rather with a giant "pipe" of magma far from the edges of plates. That makes them much more interesting than magmatism at plate boundaries, for their existence is not explained by plate tectonics. Mantle plumes seem to have their origin at the boundary between the earth's core and the mantle, and persist for very long time periods. They can be observed at the earth's surface as a "track", a wandering hotspot which is an illusion created by the movement of oceanic and continental plates on the surface of the mantle. Two famous contemporary mantle plumes are Iceland and Yellowstone Park. Mantle plumes are relevant to diamonds in an unhappy way. It is as if a very angry Hephaestus exiled to Hades has set up a giant stationary blow torch which scorches anything that moves into its path. This matters to diamonds because they grow within the diamond stability field that exists within the deep roots of cratons, continental plates with thick roots protected from the magmatism at the margins created by subduction and collisions. Diamonds end up at the earth's surface when the mantle spawns discrete, fast moving magma pulses which entrain material within the cratonic roots and erupt as kimberlite pipes. A mantle plume, however, moves through a craton laterally, not as a hot physical mass, but as a giant heat ray. While the pressure may remain the same at the various depths of a craton, the temperature will change. Diamonds that may have formed during the Archean age and have been contentedly stable since then will be transformed into graphite when the temperature of their nest changes. Because the pressure and temperature at the earth's surface is different from the diamond stability field that exists within a cratonic root, one would expect diamonds to convert into graphite. The reason they do not has something to do with kinetic energy which enables Diamonds to Last Forever. Any kimberlite which emplaced before the "arrival" of a mantle plume could be chock full of diamonds, but those which erupted after the blow-torch of Hephaestus "passed through", will be barren, though sometimes there will be octagonal "shapes" of graphite within xenoliths found in a kimberlite. Plume articles tend to be of a scientific nature and are interesting because what exactly causes mantle plumes is not decided science.
Rare Earths282142Rare Earths have no direct relevance to diamonds but they do tend to be concentrated in intrusions called carbonatites or syenites, but they are indirectly related because of the shared question of how rare earth enriched intrusions do evolve and end up at the earth's surface. The abundance of rare earth related scientific articles in the SDLRC can be construed as a cheeky reminder from Pat Sheahan to her diamond pals that diamonds aren't everything.
Redox8500Redox stands for "reduction-oxidation reaction" where electrons are lost or gained. When an atom or molecule loses electrons it has undergone oxidation whereas whatever gained the electrons underwent reduction. An atom or molecule is a reducing agent because it loses electrons which results in it being oxidized. An oxidizing agent causes other atoms or molecules to lose their electrons. Oxygen is the ultimate oxidizing agent. A dreaded topic at kimberlite conferences is oxygen fugacity which is related to rock formation in the mantle (see mineral redox buffer). Redox articles are exclusively of a scientific nature and are relevant to diamonds because they may deal with the behavior of carbon in the mantle which is, of course, from what diamonds form.
Remote Sensing112373Remote sensing is the collection of geographical information without making physical contact usually involving satellites or aircraft using sensors to passively collect data such as light reflected off the earth's surface (spectral data) or actively collect data by emitting a signal and sensing its reflection. Remote sensing is relevant to diamond exploration because it can help detect surficial anomalies related to a kimberlite pipe or dyke.
Rheology3641Rheology is a scientific term for the study of how matter flows in both a liquid and solid state. Terms like "plastic" and "viscosity" are part of rheology. It is relevant to diamonds because the mantle between the liquid outer core and the solid crust is a plastic, semi-solid material. These are exclusively scientific articles which are relevant to diamonds because somehow this hardest of naturally occurring substances forms within a semi-solid environment. Any media reference tagged with "rheology" will be worth reading because it would not dare touch the topic without attempting to make the subject intelligible to lay people.
Rifting72113Rifting occurs when a plate, namely a part of the lithosphere, undergoes stretching. This takes place constantly at oceanic spreading centers where the convection cells that drive plate tectonics force oceanic plates to drift away from each other. The result is a thinning of the oceanic crust which enables a magmatic upwelling that fills the space created as the plates drift away from each other, in effect creating new lithospheric crust. Articles tagged as "rifting", however, tend to be about cases where poorly defined forces cause continental crust to develop its own "spreading center" where the crust thins along an axis, as depicted by this rifting animation. The thinning of the crust enables magmas to ascend and exploiting structural zones of weakness, often the boundaries of the "graben" that forms as the crust pulls part. Although mantle plumes are sometimes invoked in articles tagged as "rifting", mantle plumes appear to have a mantle root that it is stationary and blasts any oceanic or continental plates that drift along. Crustal rifting, however, appears to take place independently of the mantle, with mantle magmas rushing in to fill the resulting void. Articles about rifting have little relevance to diamonds other than to signal that where a rift is present, do not expect to find any diamondiferous kimberlites that erupted after the rifting event. Areas of rifting, because they generate intrusive activity, are excellent locations for precious and/or base metals deposits to form.
Shoshonite4830Shoshonite is a basaltic igneous rock saturated with silica, low iron enrichment and with a high potassium to sodium ratio. They tend to be associated with volcanism related to calc-alkaline island-arc subduction. A shoshonite is a type of lamprophyre more commonly associated with gold deposits than diamonds.
Spectroscopy91613Spectroscopy is the study of the interaction between matter and electromagnetic radiation. Articles tagged with this key word are exclusively of a scientific nature and deal either with diamond crystals and how they reflect the visible light portion of the electromagnetic wave spectrum, or with the earth where the reflection of matter penetrating wavelengths is used to map the lithosphere and mantle. The latter is thus closely related to tomography and is only relevant to diamonds in helping identify those parts of the earth conducive to the formation of diamonds.
Spinel6230Spinel is a magnesium-aluminum mineral whose crystals can be formed in the lithosphere through metamorphism but which also form within peridotite which constitutes much of the mantle at depths of 20-120 km. The latter will include chromium and is relevant to diamonds because peridotite ends up entrained as xenoliths with kimberlitic magmas.
Stratigraphy21612Stratigraphy refers to geological layers created by sedimentation or cooling of igneous intrusions. It can also refer to differentiation within the mantle.
Structure166625Structure is one of those abstract words that can be assigned to all manner of topics. It refers to "differences" which means that articles can be about regional lineaments such as suture zones, rift boundaries and faults or about the different components of a kimberlite pipe.
Subduction48120347Subduction is a subset of "plate tectonics" which deals with what happens when oceanic and continental plates converge, namely the denser oceanic plate descends beneath the lighter continental crust.
Supercontinents172465Articles aboutSupercontinents deal with the assembly and breakup of continental plates. Articles that have been tagged with specific supercontinent names are assigned to this key word.
Tectonics514054160Tectonics deals with the processes that determine the nature of the earth's crust over time. It is a broader term than "plate tectonics" which deals with the movement of crustral plates via convection cells within the mantle. Articles tagged with the key word "tectonics" are scientific and deal with either tectonic mechanisms or specific crustal histories. They are relevant to diamonds when they deal with cratons, in particular craton formation.
Tomography121614Tomography refers to the method of imaging a section of something through the data generated by some sort of penetrating wave. It is relevant to diamonds because it enables mapping of the crust and upper mantle where diamonds are formed and magmas are generated which entrain the diamonds during their ascent. Articles tagged with the keyword "tomography" are exclusively of a scientific nature; no editor of a media publication would ever allow this topic to be visible enough to justify the 'tomography" keyword.
UHP6064654UHP refers to ultra high pressure metamorphism of rocks within the crust involving pressures that theoretically exist deeper than the 80-90 km thickness of crustal rocks. Ultra high pressure conditions emerge in subduction settings, which is relevant to diamonds because eclogite, a major source rock for diamonds, originated as an oceanic slab.
Unknown21838621571558Keywords classified as "Unknown" are those whose meaning or purpose has not yet been established in the context of the Major KeyWords that make up this index. Such keywords could be the result of spelling errors or punctuation quirks. This can arise because multiple keywords are sometimes assigned to an article which usually has a reference in one of the Major Keyword pages.This page is intended to allow the administrators of SDLRC to clean up "unknown" keywords over time, and should be ignored by other users. Because of the abundance of stray keywords we are for now not displaying any references with a keyword so far still tagged as "unknown".
Volcanism321718Volcanism is the study of the eruption of magmas at the earth's surface, with emplacement as a subset which deals with the manner in which an igneous intrusion ascends and eventually cools. Articles about volcanism can range from being about belts of volcanic rocks such as the Andes to being about the various ways in which an intrusion becomes "extrusive", that is erupts. Kimberlite pipes are formed when a kimberlitic magma erupts at the earth's surface. Articles about volcanism are relevant to diamonds when they are about the manner in which a kimberlite erupts. The degree of explosiveness depends on the gas content of the magma, the country rocks at the earth's surface, and whether or not the earth's surface was covered with water at the time of eruption. The explosive eruption event does not affect the diamonds within the magma, but it does affect the mixing of the diamonds as xenocrysts within the magma, the dilution of the magma by country rock fragments, the disaggregation of diamond-bearing xenoliths, and the eventual "shape" of the pipe.
Water211437Articles with the keyword water tend to be about the presence of water within the mantle, how it affects mantle behavior, and how water ended up in the mantle. The general theory is that oceanic slabs containing hydrous minerals that were subducted are the source of water within the mantle. The dehydration of subducting slabs contributes to magmatic fluids which can play a major role in forming ore deposits, though none containing diamonds. Meteoric Water, in contrast, involves rainwater that has worked its way back into the crust where it is otherwise known as "groundwater". Hydrothermal ore genesis models usually involve a magmatic intrusion as a heat engine that drives the circulation of meteoric water which harvests metals from the rocks through which it flows. None of this has anything to do with diamonds. Fluid Inclusion studies are used extensively in the investigation of hydrothermal systems which formed orebodies at the earth's surface, but in the context of diamonds it is tiny bubbles of water within diamonds that provide clues about the mantle's history.
Xenoliths2781815A xenolith is literally a "foreign" fragment of rock enclosed within an igneous rock. A xenolith is a foreign collection of crystals, compared to a "xenocryst" which is an individual diamond. A diamond is thus never a xenolith, but it is a xenocryst within a kimberlitic magma. A piece of harzburgite or eclogite found within a kimberlite is a xenolith, though, ironically, a diamond found inside such a xenolith is not a xenocryst because its crystal formed in conjunction with the less illustrious crystals of elements other than carbon. The operative concept is that of an already formed rock being physically introduced into a rock that is still at the formative stage, which is a magma that has not yet chilled into a igneous rock. Every magmatic intrusion will engulf already crystallized rocks (or cemented ones in the case of sedimentary rocks) as it works its way to the surface of the earth, but what makes the xenoliths found within a rapidly emplaced intrusion such as a kimberlite or lamproite so much more interesting is that they are like little suitcases of original rock plucked from the mantle as deep as 200 km. From an economic perspective mantle xenoliths are relevant to diamonds because they are the source rocks within which diamond crystals formed, but, because of the rapid ascent of kimberlitic magmas which can prevent these "suitcases" from being re-melted or otherwise transformed, xenoliths found within kimberlites are windows into the mantle.
Zircon10452Zircon is a naturally occurring silicate not to be confused with Cubic Zirconia, zirconium dioxide, which is synthesized from powdered zirconium to form a colorless crystal equivalent to a flawless D diamond but which has more "fire" than a diamond. "Fire" is the reflection of rainbow colors versus "brilliance" which is the reflection of white light or sparkle. If you see a lot of color flash from a big "diamond", it is likely a cubic zirconia which is marketed as fashion jewelry. Articles about zircon are not about diamond substitutes. Zircon crystals form within igneous rocks and usually contain uranium or thorium which enables radiometric age dating. This is very helpful for reconstructing the history of the earth based on rocks encountered at the surface of the earth's crust. Zircons are relevant to diamonds because kimberlitic magmas entrain pieces of the mantle during their ascent, some of which are preserved as xenoliths within the magmatic portion of a kimberlite pipe or dyke. Age dating of zircons recovered from kimberlites help with dating parts of the earth's mantle.
 
 

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