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Lump or vein graphite is considered to be one of the rarest commercially valuable natural graphites, and Sri Lanka is the only commercial producer of this highest quality of graphite.
Coal, diamond, and graphite are the three allotropic forms in which carbon is found naturally. Graphite crystallizes in a platy form in a hexagonal arrangement. It is metamorphic in nature, and depending on where it's found is rated into three forms - flake, crystalline, and amorphous. Flake is found as vein deposits in metamorphosed rocks; amorphous is found in metamorphosed beds of coal; and crystalline is available in veins filled with fissure.
Graphite has a blackish-to-grayish color, and due to its greasiness and softness, it leaves a black mark when touched by hand. It is an excellent conductor of electricity and heat. Graphite can withstand extremely high temperatures, and is not affected by a majority of reagents and acids. This property gives advantages which are unique and peculiar to graphite.
Graphite is found all over the world in its natural form, and in high quantity as well. It has been in use since ancient times, and has a wide range of applications in the modern world too. South Korea is said to be the largest producer of graphite in the world, with Austria coming a close second.
Crystalline Flake Graphite
Large crystals or coarse to fine flakes
More expensive than amorphous graphite
- Crystalline flake graphite is known to show very low resistance to electrical conductivity. More the flaky particles, lesser the resistance and bulkier the density.
- This particular characteristic of flake graphite makes it useful in the manufacturing of carbon electrodes, brushes, and plates needed in dry cell batteries and the electrical industry.
- However, these days, amorphous graphite has replaced flaky graphite in the production of brushes and plates.
- Flake graphite is also commonly used in manufacturing crucibles.
- It is used in foundry-facing to disallow molding sands from sticking to cast articles.
- High-grade graphite in amorphous and crystalline form, having the ability to remain suspended in oil, is used in the manufacturing of lubricants. Irrespective of the working condition, graphite shows very low friction, which is why it is used in lubricants. It keeps the moving surface cool and minimizes the friction.
- Graphite in its amorphous form is used in the manufacturing of lead used in pencils. Amorphous graphite is preferred as it leaves a dark streak on paper. Finer the powder, darker the smear. In case the graphite is flaky, the smear loses its darkness.
- It is used in several lubricant products, such as grease and forging lubricants.
- In applications where high amounts of ash is preferred, amorphous graphite is used. The ash content in amorphous graphite has the ability to provide the soft rubbing abrasion needed to clean the surfaces on which it is applied.
- It also has applications in powder metallurgy and grinding wheels.
- Graphite is used as a carbon raiser in the production of steel that gives steel its strengthening characteristic.
- It is also used for making printing electrotypes. A thin layer of powdered graphite is applied on the wax impressions made, on which copper is deposited. The role of the thin layer of graphite is to provide negative electrical connection so that the process of electrolysis goes on smoothly, depositing copper on it.
- In production of paints, the powdered form of lump graphite is used, and since graphite is a natural water-repellent, it is the best choice for giving a protective coating on wood.
- It is used in advanced, high-friction applications such as car brakes and clutches, because of its high thermal and electrical conductivity.
Natural graphite can be processed into synthetic graphite, which is useful for higher value applications like lithium-ion batteries, but the process of synthetic graphite production is very expensive.