From mine to market: creating a
vertically integrated supply chain for
high-specification graphite products

About Graphite

Graphite is a grey to black form of carbon with a metallic lustre. It is naturally occurs on Earth in metamorphic rocks such as marble, schist, gneiss and phyllite and is considered as one of the most versatile non-metallic minerals in the world.

Graphite is an excellent conductor of electricity and heat. It has the strength to resist chemical attack and sustain to temperatures exceeding 3,600°C, enabling it to have considerable commercial applications in the manufacturing and metallurgical industries.

Graphite is usually found in association with feldspar, mica, quartz, pyroxene, rutile, pyrite, tourmaline and apatite. Its powders can be split into two main categories: natural and synthetic.

Natural Graphite

Natural Graphite is usually found in metamorphic rocks and is has unique grain sizes and purity. To increase graphite purity, the mineral is treated by thermal or chemical purification processes. There are three common forms of natural graphite: amorphous, flake and vein.

1. Amorphous Graphite

Amorphous is a microcrystalline form of graphite. It has a carbon content of 70-85% and is the most abundant form of graphite making up around 60% of the market. Amorphous graphite is a seam mineral typically has a higher ash count than other natural forms of graphite. Amorphous graphite is normally used in lubricant products such as greases and forging lubricants.

2. Flake Graphite

Flake graphite (is also called crystalline graphite), consists of multiple layers of stacked graphene with a flake shape. It occurs naturally in metamorphic rocks, has a carbon content of 85-97%, an ash content of up to 15% and graphitisation up to 95-100%. Flake graphite is the feedstock for spherical graphite, expandable graphite and graphene. It is common, making up about 40% of the market.

3. Vein Graphite

Vein graphite (also called lump graphite) typically has a carbon content of 90%, a purity that can reach 98% in the ground, and it appears as large lumps of solid graphite. Vein graphite is the rarest and most valuable form of graphite. It is usually found in high grade deposits and is highly sought after by both miners and suppliers. This is because for mining, the higher the grade, the lower the milling and refining cost. For suppliers it offers more flexibility in end-product applications.

Synthetic Graphite

Synthetic graphite is a man-made form of graphite derived by using high-temperature treatment on amorphous carbon materials. Synthetic graphite is processed at ultra-high temperatures (up to degrees to 3,000 degrees), and impurities contained in the precursor carbons are significantly reduced during processing. The carbon content varies widely (typically ranging between 98-99.99%).

1. Primary Synthetic Graphite

Primary synthetic graphite is obtained by transformation of carbonaceous precursor into graphite through an industrial process, called graphitisation (temperature >3000°C).

Graphitisation is a microstructural change which can occur in carbon or low alloy steels that are exposed to elevated temperatures, between approximately 425°C and 600°C, for long periods of time. Simply stated it is the process of converting material into graphite by a heating process.

2. Secondary Synthetic Graphite

Secondary synthetic graphite is also obtained by transformation of carbonaceous precursor into graphite through a graphitisation process.

After crushing, grinding, screening and sieving of the dry raw materials (usually calcined petroleum coke), these are mixed with the tar pitch and moulded in blocks. Blocks are then baked or carbonised at 800-1330°C and graphitised at 2600-3000°C in furnaces.

These blocks are then machined in order to get electrodes of the shapes and sizes required by the metal industry. During this machining process graphite powders are generated. This by-product of the production of graphite electrodes is called secondary synthetic graphite.