It takes a smart dog to find hidden treasures

Graphite:  the other key battery mineral

Graphite: where being a big lump or a just flake can be good!

Graphite is a form (allotrope) of carbon. named by Abraham G Werner in 1789 from the Ancient Greek (graphō), "to draw/write".  It is one of the three allotropes of element carbon that exist in nature, the other two being coal and diamond.  Unlike diamond, graphite is an electrical conductor, making it a semimetal. Graphite is the most stable form of carbon under standard conditions. Graphite may be considered the highest grade of coal, just above anthracite and alternatively called meta-anthracite, although it is not normally used as fuel because it is difficult to get it to ignite. 

It has black to steel grey color, usually leaves a black streak on the hand when touched because of its extreme softness and greasiness. It is opaque even in the finest particles. Graphite is a good conductor of heat and electricity. It has high refractoriness. It can stand a temperature upto 3000ºC in an inert atmosphere though in the presence of oxygen it burns between 620ºC to 720º C. It is unaffected by most of the acids and reagents but yields graphitic acid on treatment with a mixture of potassium nitrate and nitric acid.

There are two major types natural and synthetic (artificial).

 Naturel graphite is of metamorphic origin and usually found as veins, lenses, pockets and as thin laminae disseminated in the gneisses, schists and phyllites. Depending upon the mode of occurrence and origin, it is graded into three forms:

Flake - found in metamorphosed rocks as vein deposits.(approximately 90% carbon)

Crystalline (lumpy) - found as fissure filled veins.(approximately (95+% carbon)

Cryptocrystalline (amorphous) - form in metamorphosed coal beds.(approximately 85% carbon)

Synthetic graphite is also called artificial graphite, is a man-made form of graphite (approximately 98+% carbon). It is obtained by processing a feed stock (often petroleum coke). After crushing, grinding, screening and sieving of the dry raw materials, these are mixed with the tar pitch and molded in blocks. Blocks are then baked or carbonized at 800-1330°C and graphitized at 2600-3000°C in furnaces. During this processing graphite powders are generated.  This byproduct of the production of graphite is called secondary synthetic graphite.

 Uses of Graphite

 Graphite is used in a wide variety of applications: refractories, carbon brushes, lubricants, steelmaking, metal casting, brake linings, fuel cells, batteries, and pebble nuclear reactors. The largest market for graphite is in traditional industries like carbon raiser for steel and refractories.

 Below are reported the main applications of graphite.

Steel, foundries, & refractories – 41%

Automotive parts – 14%

Lubricants – 14%

Carbon brushes – 11%

Batteries – 10%

Others – 10%

  Metallurgical Industry: Refractories are probably the largest consumer of natural graphite powder due to its ability to increases the thermal shock and corrosion resistance. The most import graphite use in steel and iron industry is in magnesia-carbon bricks, which can resist the corrosion caused by impurity on the top of molten metal. Graphite is also used as protective layer on the top of molten copper and other non-ferrous metal; this topping prevents oxidation that can occur when the molten metal bath comes in contact with air.

 Steel industry: In steel-making graphite is used to increase the carbon content of steel. Graphite is also required in liners for ladles, crucible and in thermal blanket for the continuous steel casting process.

 Lubricants: Graphite can be used as a solid lubricant or dispersed in water or in oil and grease. Water based dispersion are exploited in the production of seamless tube or in the hot metal forming industry (forging, extrusion, etc.).

 Friction Materials: Graphite powders are used in brake pads in automotive, heavy-duty vehicles (trucks, trains, airplanes) and in industrial machines. Graphite has to provide the required level of friction coefficient at different operant conditions. it also contributees to temperature vibration, noise and wear control.

 Carbon Brushes: Graphite is a main component of carbon brushes used in the majority of electrical motors. Graphite fixes the electrical conductivity of the brush and also contributes to reduce wear while lubricating and increasing the mechanical strength.

 Batteries: Due to their electrical conductivity graphite powders are used in zinc-carbon batteries, alkaline batteries, lithium-ion batteries, fuel cells and super capacitors.  In alkaline batteries graphite is used as a conductive additive in the cathode, together with electrolytic manganese dioxide (EMD). In lithium-ion rechargeable batteries, graphite is used as active material in the negative electrode of lithium and as a conductive additive in the positive electrode.  Most bipolar plates of fuel cell bipolar are manufactured by compression moulding using graphite and polymer compound (graphite content:  75-85%). Graphite is also used as a coating for metallic bipolar plates to avoid corrosion.

 Thermal conductive and electrical conductive polymers:  Graphite finds wide applications as a polymer additive thanks to its properties: low friction, lubricating (self-lubricating polymers), chemical inertness, high thermal conductivity, thermal stability and electrical conductivity. In alternative to metal flakes or powders, graphite can increase the thermal conductivity of polymers when the heat generated from a device needs to be evacuated resulting in temperature reduction. Some end-use applications are: heat sink, geothermal pipes, LED light sockets, heat exchanger, temperature sensors, etc.

 Various applications: Graphite in also used in various other applications: pebble bed nuclear reactors, seals, foils, coatings, paints, pencils, ceramics, catalyst support, synthetic diamond and hard metals.

How does Graphite form: from pressure & temperature

Review: What is Graphite?

Graphite is a soft, crystalline form of carbon, and while it shares the same chemistry as diamond the two have very different physical properties.  Diamond forms in the mantle under extreme heat and pressure. Most graphite found near Earth's surface was formed within the crust at lower temperatures and pressures. Graphite and diamond share the same composition but have very different structures.

The carbon atoms in graphite are linked in a hexagonal network that forms sheets that are one atom thick. These sheets are poorly connected and easily cleave or slide over one another if subjected to a small amount of force. This gives graphite it’s very low hardness, its perfect cleavage and its slippery feel.

In contrast, the carbon atoms in diamond are linked into a frameworks structure. Every carbon atom is linked into a three dimensional network with four other carbon atoms with strong covalent bonds. This arrangement holds the atoms firmly in place and make diamond an exceptionally hard material.

Graphite exhibits both metallic and non-metallic properties. The metallic properties include thermal and electrical conductivity, while the non-metallic properties include inertness, high thermal resistance, and lubricity. Some of the major end uses of graphite are in high-temperature lubricants, brushes for electrical motors, friction materials, battery and fuel cells, and pencil "lead".

How does Graphite occur: Geologic Occurrence

Graphite is a mineral that forms when carbon is subjected to heat and pressure in Earth’s crust and in the upper mantle. Pressures in the range of 75,000 pounds per square inch and temperatures in the range of 750 degrees Celsius are needed to produce graphite. These correspond to the granulite metamorphic facies. 

Graphite from Regional Metamorphism (Flake Graphite)

Most of the graphite seen at Earth’s surface today was formed at convergent plate boundaries where organic-rich shales and limestones were subjected to the heat and pressures of regional metamorphism. This produces marble, schist and gneiss that contains tiny crystals and flakes of graphite. 

When graphite is in high enough concentrations these rocks can be mined, crushed to a particle size that liberates the graphite flakes and processed by specific gravity separation or froth flotation to remove the low density graphite. The product produced is known as “flake graphite”. 

Graphite from Coal Seam Metamorphism ("Amorphous" Graphite) 

Some graphite forms from the metamorphism of coal seams. The organic material in coal is composed mainly of carbon, oxygen, hydrogen, nitrogen and sulfur. The heat of metamorphism destroys the organic molecules of coal, volatilizing the oxygen, hydrogen, nitrogen and sulfur. What remains is a nearly pure carbon material that crystallizes into mineral graphite. 

This graphite occurs in “seams” that correspond to the original layer of coal. When mined the material is known as “amorphous graphite”. The word “amorphous” is actually incorrect in this usage as it does have a crystalline structure. From the mine this material has an appearance similar to lumps of coal without the bright and dull banding. 

Amorphous graphite is the most abundant graphite form and the least valuable. Deposits of amorphous graphite are often found with coal deposits; however, separation of amorphous graphite from coal is a far from trivial process and results in a lower quality product.

Graphite from Hydrothermal Metamorphism (Lump Graphite)

A small amount of graphite forms by the reaction of carbon compounds in the rock during hydrothermal metamorphism. This carbon can be mobilized and deposited in veins in association with hydrothermal minerals. Because it is precipitated it has a high degree of crystallinity and that makes it a prefered material for many electrical uses. 

Graphite in Igneous Rocks and Meteorites 

Small amounts of graphite is known to occur as a primary mineral in igneous rocks. It is known as tiny particles in basalt flows and syenite. It is also known to form in pegmatite. Some iron meteorites contain small amounts of graphite. These forms of graphite are occurrences without economic importance. 

 Synthetic Graphite

 “Synthetic graphite” is made by heating high carbon materials like petroleum coke and coal tar pitch to temperatures in the range of 2500 to 3000 degrees Celsius. At these high temperatures, all volatile materials and many metals in the feedstock are destroyed or driven off. The graphite that remains links into a sheet-like crystalline structure. Synthetic graphite can have a purity of over 99% carbon, and is used in manufactured products where an extremely pure material is required. 

 Graphene & Beyond  

One single layer of graphite is called “graphene sheet”. Expandable graphite and graphene are normally produced from flake graphite. Expandable graphite is formed by expanding the carbon layers of flake graphite and introducing atoms or small molecules to this space. Expandable graphite is primarily used as a flame retardant; in comparison to other flame retardants it is free from halogens and heavy metals, is low cost and suitable for a wide range of applications. Graphene that could be obtained starting from graphite is a relatively new discovery and as of today it is produced in limited quantities, but it is considered a very promising material to be exploited in various applications like battery, thermal management, polymer composites, sensors, flat-panel displays, etc.


MIke Albrecht, P.E.

o   40+ years’ experience in the mining industry with strong mineral processing experience in precious metals, copper, industrial minerals, coal, and phosphate

o   Operational experience in precious metals, coal, and phosphate plus in petrochemicals.

o   Extensive experience performing studies and determining feasibility in the US and international (United States, Canada, Mexico, Ecuador, Columbia, Venezuela, Chile, China, India, Indonesia, and Greece).

o    E-mail: