Graphite

Graphite

Composed exclusively of the element carbon, as with diamond, graphite is a semimetal native element mineral and an allotrope of carbon, having said that, graphite and diamond are interesting minerals with a chemical identity! Physically being different, they are called as polymorphs. Minerals with equivalent chemistry and different crystal structures are known as polymorphs. While diamonds are brilliant and transparent, graphite is opaque and metallic.

They are considered as the highest grade of coal just above anthracite and otherwise called meta-anthracite, even though it is used as fuel for the reason that it is quite difficult to ignite. Under standard conditions, graphite is the most stable form of carbon. Consequently, for defining the heat formation of carbon compounds, it is used in thermo chemistry as the standard state.

Graphite Varieties

? Crystalline flake graphite

? Amorphous graphite

? Lump graphite

Graphite

Natural graphite uses

The use of graphite dates back to B.C, in the 4th millennium B.C. During the Neolithic Age in southeastern Europe, the Marita culture graphite was used in a ceramic paint for decorating pottery. The occurrence of natural graphite is consumed for:

? Refractories

? Batteries

? Steelmaking

? Expanded graphite

? Brake linings

? Foundry facings and

? Lubricants

Graphene occurs naturally in graphite and it is one of the strongest substances known with unique physical properties. Prior to its functionality i.e. usage in any industrial processes, it requires some technological development for separating it from graphite.

Other uses of graphite include: zinc-carbon batteries, in electric motor brushes. In order to create a heat resistant protective coating, railroads would habitually mix powdered graphite with waste oil or linseed oil for the exposed portions of a steam locomotive's boiler, such as the smoke box or lower part of the firebox. With a historical reference, it was called the black lead or plumbago.

Graphite is extracted mainly depending on the two things, they are the degree of weathering of the ore and the proximity of the ore to the surface. They are classified into microcrystalline graphite, macrocrystalline graphite and lump graphite based on the physical and chemical properties. Graphites are extracted by two techniques: the open pit method and the underground method. The economic value of the ore will determine the type of the mining to be used.

Open pit mining

Open pit mining is generally used where the ore is lying close to the earth and the layer of surface material covering the ore is thin. Microcrystalline or flake graphite and macro crystalline graphite are generally extracted by the open pit mining as they close to the earth. Quarrying is one of the methods of surface mining where the rocks are broken either by drilling or by using dynamite explosives to obtain the graphite. Drilling and blasting are used to break down the large and hard rocks. They also allow the compressed air or water to break the rocks. The graphite obtained from this process is crushed and ground before being subjected to flotation. The extracted graphite is then picked through the hand tools and carried out for further processing.

Underground mining

Underground mining is done to reach the deepest ores. For the extraction of the ore in the underground mining, several methods like drift mining, hard rock mining, shaft mining and slope mining are employed. These are considered based on the financial and economical reasons. Borehole mining that is common to both open pit mining and underground mining is done by drilling the ore to reach the ore. It makes a slurry using the water through a tube, the water and the mineral is then pumped back to the storage tank for further processing.

Drift mining is a gravity aided extraction where the horizontal shafts are made lower than the mineral vein. It is generally done in the mountain region to extract the minerals.

Shaft mining is done when the ore is present in the deepest depth. Miners and specialised equipment can be moved in and out through the shafts, while different shafts are used for transportation of ore that are extracted. There will be a seperate air shafta which is given particularly for extraction.

Slope mining is employed when graphite ore is present parallel to the ground. The slanted shafts are laid to minimise the transportation.

Beneficiation of graphite

Beneficiation is done to improve the economic value. In this process, the gangue materials surrounding the ore is removed to result in a higher grade product. Then in milling the incoming graphite products can be carefully preserved. The size distribution of the carbon content of the graphites are measured and they are used accordingly. Now many mining companies are trying to bring new and improved technologies to identify and extract the graphite.