Graphite

Graphite is a crystalline form of the element carbon with its atoms arranged in a hexagonal structure. It is the most stable form of carbon under standard conditions and is unique among non-metals for its high electrical conductivity and lubricity.

Description of what it is like

• Appearance: Steel-gray to black, metallic luster.
• Texture: Greasy or slippery to the touch; leaves a black mark on skin or paper.
• Behavior: Very soft (Mohs hardness 1-2), can be easily flaked or ground into powder.

Origin and where to find it

• Environments: Found in metamorphic rocks such as marble, schist, and gneiss. Often occurs as flakes or veiny masses.
• Signs: Black, shiny streaks in rock; slippery feel when rubbed.
• Natural/Synthetic: Naturally occurring mineral; synthetic version is produced from coke.

Minimum processing required

• Mining: Extraction from ore.
• Crushing and Grinding: Breaking the rock to release graphite flakes.
• Flotation: Using water and oils to separate lightweight graphite from heavier waste rock.
• Purification: Acid treatment to remove remaining mineral impurities if high purity is needed.

Tools needed to work on it

• Hammers and chisels for extraction.
• Mortar and pestle or ball mill for grinding.
• Flotation tanks (simple containers with agitation).
• Crucibles for high-temperature processing.

Common forms of use

• Powder: Used as a dry lubricant for locks and machinery.
• Blocks/Rods: Used as electrodes in furnaces or electrolysis.
• Clay-mix: Mixed with clay to create pencil leads.
• Crucibles: Mixed with clay to withstand extreme heat for melting metals.

Possible substitutes

• Molybdenum Disulfide: Another dry lubricant (if available).
• Charcoal: Can be used for simple drawing or as a carbon source, but lacks conductivity and lubricity.
• Copper: For electrical conductors, though copper melts at much lower temperatures than graphite.

Limitations and common failures

• Brittleness: Solid graphite blocks are brittle and can snap under tension.
• Oxidation: Burns slowly in air at very high temperatures (above 700°C).
• Anisotropy: Properties (like conductivity) vary depending on the direction of the crystal layers.

Risks and safety

• Dust Inhalation: Fine graphite dust can cause respiratory issues (graphitosis) over long-term exposure.
• Conductivity: Graphite dust can cause short circuits in electrical equipment.

Related materials

• Carbon: The element that composes graphite.
• Coal: Another carbon-rich mineral.
• Charcoal: Amorphous carbon produced from wood.
• Clay: Often mixed with graphite for pencils and crucibles.