Types of Graphite - Amorphous, Flake and Vein

Coal and Related Carbon Resources / Lignite, Graphite, Graphene, & Carbon Uses

Date posted: 04/19/16

Charlotte McLeod reports that graphite has a layered, planar structure, with carbon atoms arranged in a honeycomb lattice. It is because of this unique structure that graphite has such a stellar combination of properties, for example, it is flexible, highly refractory, chemically alert and has high thermal and electrical conductivity. Those characteristics allow graphite to be used in a variety of places, including brake linings, foundry operations, lubricants, refractory applications and steelmaking. However, not all graphite is suitable for all applications. Indeed, there are three main types of graphite, and in many cases specific applications require one type in particular, i.e., flake, amorphous, and vein. Flake graphite occurs as isolated, flat, plate-like particles with either hexagonal or angular edges. It is found in metamorphic rocks, such as limestone, gneiss and schist, either uniformly distributed through the body of the ore or in concentrated, lens-shaped pockets. Flake graphite is the type of graphite that those in the industry are most interested in. That is because it is the type of graphite that Tesla Motors will require for its lithium-ion battery gigafactory. Other companies with megafactories in the works will also need it. Flake graphite comes in 4 basic sizes, jumbo, large, medium and fine. Amorphous graphite is found as extremely small, crystal-like particles in beds of mesomorphic rocks like coal, slate and shale, and its carbon content depends on that of its parent material. When found in coal it is the result of the thermal metamorphism of coal, and is referred to as meta-anthracite. However, unlike coal, amorphous graphite is not used as fuel as it is difficult to ignite. Vein graphite, also referred to as lump graphite, is believed to have hydrothermal origins and occurs in fissures or fractures, appearing as massive platy intergrowths. Graphite in this form is found all over the world, but is only currently mined in Sri Lanka.