Graphite potential in Greenland E R O D Graphite potential in Greenland N A Y G O L O E G Graphite is the most common natural - humic or organic material. These syn - Crystalline flake graphite ly occurring form of crystalline carbon. genetic deposits yield either microcrys - The crystalline flake graphite is the com - It has special characteristics due to its talline or flake graphite (see section on mercially most important form of natural crystallographic structure, making gra - types of graphite), depending on the graphite. It occurs less commonly in nature phite a very important industrial min - metamorphic grade of the host rock. In than microcrystalline graphite but more eral with many applications including low-grade rocks, graphite deposits occur commonly than vein graphite. It occurs in refractories, electrodes and crucibles, as black shales, graphitic slates or graphi - metamorphic rocks such as marble, gneiss - brake linings, lithium-ion batteries, tised coal. For high-grade rocks, graphite es and schist. It consists of many graphene etc. The production of total graphite deposits occur in gneisses, quartzites or sheets stacked on top of each other with in 2017 was 1.2 mio. tonnes. A conser - granulite facies rocks. weak bonds holding them together and vative prediction is that the demand therefor occurs as separate flakes. The for flake graphite will rise 50% by Magmatic sources of graphite are carbon- flake size and crystallinity depends on the 2025 to about 900,000 tonnes per bearing fluids (or, less commonly, melts). The grade and temperature of the metamor - year, especially due to the production graphite deposits form through rapid depres - phism, with amphibolite to granulite facies of lithium batteries for electric cars. surisation and quenching of CO 2/CH 4-rich metamorphism producing the important fluids, which trigger rapid crystallisation of economic deposits. The large crystals allow In November 2017, a workshop on the fine-grained graphite within breccia matrixes it to be used in more high-valued applica - ‘Assessment of the graphite potential in and fractures in the walls. These deposits tions, such as refractories, foundries and, Greenland’ was arranged jointly by the yield vein graphite. to some extent, in lithium-ion batteries Geological Survey of Denmark and Green- and other battery types. land (GEUS) and the Ministry of Mineral Carbonatitic sources of graphite are Resources (MMR), Government of Green- limestones, marbles and calc-silicate rock. Vein graphite land. This workshop deviated from the These rock types can undergo decarbona - Vein graphite is the rarest, most valuable standard resource assessment procedures tion reactions and thereby form carbonate and highest-quality type of natural gra - applied in previous workshops, because rocks with graphite deposits. These phite. It occurs in solid lumps in veins no statistic grade/tonnage model has been deposits yield either microcrystalline or along intrusive contacts. Vein graphite established. Instead the focus of the work - flake graphite, depending on the meta - results from deposition of carbon-bearing shop was to present and discuss: 1) the morphic grade of the host rock. fluids (or melts) that are channelled graphite value chain, 2) the Nordic gra - through fracture systems. The most eco - phite projects and operations, 3) the cru - nomic significant vein deposits are from cial parameters for graphite occurrence Types of graphite high-grade upper amphibolite to granulite evaluation, and 4) known graphite occur - Natural graphite facies environments. Vein graphite is a rences in Greenland and their potential. Microcrystalline graphite (also known niche market of c. 5,000 tonnes/year. It is as amorphous) used for electrical applications, friction This edition of Geology and Ore provides Microcrystalline graphite is the most abun - products and powdered metal. an overview of: 1) the sources of graphite dant form of graphite but also the lowest- and the deposit types, 2) the graphite priced graphite. This form of graphite Synthetic graphite products, and 3) known graphite occur - commonly occurs as micro-crystalline par - Synthetic graphite is manufactured from rences in Greenland. A GEUS report docu - ticles fairly uniformly distributed in weakly calcined petroleum coke, coal tar pitch, menting results from the workshop is metamorphosed rocks, such as slates, or anthracite, recycled synthetic graphite or available. graphite beds of sedimentary origin. The natural graphite. It is very costly to pro - grade varies and reflects the carbon con - duce synthetic graphite as its precursor tent of the original sediment. Some micro - material has to be baked at high tempera - Sources of graphite crystalline graphite deposits are formed tures of >2500 ˚C for several days. The syn - Graphite deposits can be derived from from contact metamorphism, whereas thetic graphite is of very high quality and biogenic, magmatic or carbonatitic sour - others are a result of regional metamor - has a purity of 99.99%. It is used in high- ces. phism. Micro-crystalline graphite is mainly end products such as electrodes in steel used for lubricants, refractory products, production, and in aluminium production, Biogenic sources of graphite are restrict - paints, drilling mud etc. in lithium-ion batteries for electric vehicles ed to sedimentary environments and the and in the electrical, chemical, nuclear, accumulation of algae, phytoplankton, mechanical and aerospace industries. 2 GRAPHITE POTENTIAL IN GREENLAND E R O D N A Y G O L O Physical and chemical properties E G The three forms of carbon (charcoal, Advance Bugt graphite and diamond) are distinguished by chemical and physical properties. The gravities of charcoal, graphite and dia - mond are 1.3 – 1.9 g/cm 3, 2.266 g/cm 3 Gable and 3.5 g/cm 3, respectively. Graphite has Gletscher a hardness of 1 to 2 (Mohs scale), which makes it a soft and flexible material. It is Graphite occurrence heat resistant to about 3000 ˚C (in a re - Palaeogene mac volcanics ducing atmosphere) and it is an excellent Phanerozoic sediments conductor of heat and electricity. Graphite Palaeozoic granites is chemically inert, environmentally friend - ly, resists chemical attack by most Mesoproterozoic alkaline plutons reagents and is infusible in most common Langø Mesoproterozoic supracrustals fluxes. Flake graphite has a very high crys - Palaeoproterozoic infracrustal rocks tallinity and a strong anisotropy along the Palaeoproterozoic supracrustal rocks graphene layers causing lubricity. Other Niaqornat Late Archaean granites molecules can intercalate be tween the Archaean basement graphene layers and give it expandable Ilugissoq properties. Qaarsut Graphite products Giesecke Natural graphite is characterised by many Akuliaruseq parameters, the two most important ones Maligiaq for commercially traded flake graphite being purity (carbon content) and particle Utoqqat size distribution (PSD). High carbon con - Kangikajik tent products have been processed in sev - eral steps for purification and are, there - Auppaluttoq fore, more expensive. Large flakes are more rare and, therefore, attracts higher prices. In contrast, smaller sizes of scree - ned product are cheaper as this material is more abundant. Typically, screened prod - ucts are commercially available in classes Grænseland from –200 mesh (75 mi crons) to +32 Kangerluk 250 km mesh (500 microns). Amitsoq Illukulik Graphite concentrate, called category 0 product, is usually not sold on the market. Sissarissoq + Kalaaq Instead, the concentrate is screened into Main lithostratigraphic units in Greenland with location of known graphite occurrences. standard products of different mesh grades (categories 1 and 2). Mines typical - ly have their own advanced screening If the graphite is subsequently milled to a cal graphite, lubricants and graphene have plant and convert their concentrate direct - so-called micronised product, it is classi - a more complex production process. ly into standard products. fied as a category 3 product. These category 4 products are the most expensive. Prices are typically opaque and Special-value added products such as individually agreed to be tween processor/ expandable or expanded graphite, spheri - trader and customers. 3 GRAPHITE POTENTIAL IN GREENLAND E R O D N A Y G O L situated at Amitsoq near Nanortalik, O South Greenland. It was in operation E G between 1914 and 1924 and it produced c. 6,000 tonnes of ore at an average grade of 21% Cg (graphite in carbon). Graphite occurrences in Greenland Occurrences of graphite and graphite schist are reported from many localities in Greenland. South Greenland Amitsoq The Amitsoq Island north of Nanortalik, in South Greenland, encompasses the former Kalaaq Amitsoq graphite mine. Several graphite showings are also reported in the sur - rounding Nanortalik region (see below). The graphite at Amitsoq is hosted by graphitic schists embedded in strongly- sheared cordierite-sillimanite-biotite gneisses. The host rocks are Palaeo - proterozoic high-grade metamorphic Sissarissoq gneisses of the Ketilidian Psam mite zone. The graphite content ranges from c. 20– 35%, with an overall mean graphitic car - bon content of 28.7%. The graphite exists in various morphologies, ranging from fine-grained specular forms to large dis - crete crystals, to agglomerations, which Geological map of known graphite occurrences in the Nanortalik region (Source: Jeroen van Gool). span areas of up to 15 m in size. The average flake size is 0.2