What is graphite?
Graphite is a natural mineral made up of only Carbon (C), like diamond, which shares the same chemical composition. However, these two minerals differ in the arrangement of their carbon atoms. Diamond stands out for its hardness while graphite is rather soft since it consists of loosely linked non-compact hexagonal rings called graphenes.
Graphite is the only non-metallic mineral that is electrically conductive. It also benefits from high thermal conductivity. Its texture is rather greasy, which allowed ancient peoples to already use graphite to write. This is where the word graphite comes from: the Greek word “graphein” which means to write.
Graphite is mainly found in one of threee forms
|Flake graphite||The most common graphite form is flake. Flakes (displaying a morphology of small flat pieces) represent about 50% of the world’s graphite production. The market value of graphite is controlled by high purity flakes between 85% and 99% C. Nouveau Monde’s graphite will be offered in this form.|
|Amorphous graphite||Amorphous graphite is made up of crystals, so thin that can not be seen by the naked eye. Its is less pure than flake graphite, varying between 60% and 90% C. This explains why this form holds the lowest market value.|
|Vein graphite||Vein graphite is much rarer, accounting for only 1% of world production and being mined in exclusivelly in Sri Lanka. Sold in pieces, its crystallization varies between very fine crystals and very large flakes of up to 1 cm.|
There are four known formations that produce each a particular graphite form.
1- Metamorphic : advanced metamorphism flake graphite
3- Metasomatic contact amorphous graphite,
4- Hydrothermal vein: vein graphite
Metamorphic deposits are formed by concentration and crystallization of carbon in place, both in silica rich rocks and in carbon rich sedimentary rocks, during a phase of metamorphism that can extend to an entire region. These deposits contain flake graphite. In Quebec, the Grenville orogeny has favored the formation of graphite deposits associated with gneisses, quartzites and schists on the North Shore (Lac Knife, Lac Guérêt) or associated with graphitic marbles in the Mont -Laurier (Lac-des-Îles) and Gatineau regions.
Metamorphosed deposits are formed by contact metamorphism of sediments rich in carbonaceous organic matter (bitumen, coal). The rocks associated with these deposits are quartzites, shales, phyllites and metagrauwackes. Contact deposits also include metasomatic “skarn” contact deposits. These develop in contact with carbonate rocks and plutonic rocks by crystallization of organic carbon or reduction of initial CO2. Amorphous graphite is found in contact deposits.
Hydrothermal vein deposits are formed from post-magmatic solutions rich in CO2. They are generally associated with stratospheric flake graphites producing an enrichment of vein graphites. They can produce amorphous and flake graphites which are generally very heterogeneous in purity, in nature and in crystal size. Among these are the very high purity deposits of Sri Lanka. In Quebec, these deposits are in the Outaouais (old mines Miller and Walker).
Although historically known for its writing properties, graphite is now used in many other industries. With a melting point of 3927 ° C, graphite is mainly involved in the manufacture of refractory materials and in metallurgy. Graphite is a lubricant that also serves in foundries as coating for molding parts, thus facilitating the separation of the object from its mold.
The automotive industry also uses a lot of graphite, both for the manufacture of brake linings and brake segments and for lubricants that perform at several temperatures. Today, graphite is increasingly recognized as one of the key elements in the manufacture of lithium-ion batteries for electric vehicles. For example, Nissan’s Leaf electric automobile model requires a battery that contains 40kg of graphite. (Source: https://en.wikipedia.org/wiki/Graphite) Its demand has been growing over the last 30 years to serve the production of batteries of other elements such as cell phones and laptops.