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Material World
Mineral · C

Graphite

Carbon in stacked sheets — soft, slippery, electrically conductive, and chemically identical to diamond.

Electrical conductor Refractory

Graphite is carbon in flat hexagonal sheets, strongly bonded within each sheet and only weakly held between them. Those weak interlayer forces are the reason it is soft, why it marks paper, and why it works as a dry lubricant: the sheets slide over one another with very little resistance.

Everything that makes graphite useful and everything that makes diamond useful comes from the same element in a different arrangement. It is the clearest available demonstration that composition alone does not determine a material's properties.

Why it behaves as it does

Graphite is soft and conducts electricity for the same structural reason, and both follow from how the carbon is bonded. The atoms lie in flat hexagonal sheets, strongly bonded within each sheet and held to the sheets above and below only by weak forces. The sheets slide over one another under almost no load, which is why graphite feels slippery, marks paper, and works as a dry lubricant.

Within each sheet, one electron per atom is not tied up in the bonds and is free to move across the plane. That is what makes graphite an electrical conductor while diamond, which uses all four of each atom's electrons in fixed bonds, is an insulator. The two are the same element in different arrangements, and every difference between them comes from that.

Name origin

From Greek graphein, 'to write' — named in 1789, well after the substance had been in use for writing for two centuries under the mistaken name plumbago.

How it forms

Graphite forms when carbon-bearing sediment is metamorphosed. Organic matter buried in mud is progressively stripped of hydrogen and oxygen by heat and pressure until only carbon remains, and given enough of both it orders itself into the layered structure that makes graphite what it is.

The best flake graphite comes from high-grade metamorphic rocks — marble, schist and gneiss — where the process ran to completion. Graphite also crystallises directly from carbon-bearing fluids in veins, and small amounts occur in some igneous rocks, but the metamorphosed-sediment route accounts for essentially all commercial production.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is a polymorph of

  • Diamond — mineral · both pure carbon; cubic versus hexagonal layered structure Wikidata

contains

is used as

is commonly confused with

  • Diamond — mineral · identical composition, opposite properties — the standard illustration of why structure matters
  • Molybdenite — mineral · the reason molybdenite is named after lead: it, graphite and galena were long taken for one substance

is a component of

  • Schist — rock · in metamorphosed carbon-rich sediments, and the source of flake graphite — the form batteries and refractories want
  • Refractory brick — material · in magnesia-carbon brick for steel ladles, where the carbon stops the slag wetting the grain and is why the lining survives the pour

is an alternative to

  • Molybdenite — mineral · as a dry lubricant. Both are layered structures that shear easily, and molybdenite keeps working in vacuum where graphite fails — graphite needs adsorbed water to be slippery at all, which is why it stopped working on spacecraft

is used in

  • Lithium-ion cell — object · the anode, unglamorous and the largest component by mass after the cathode
  • Pencil — object · the core, and it marks paper because the carbon sheets shear off under almost no pressure — the same property that makes it a lubricant

is associated with

  • The wartime materials programmes — event · reactor-grade graphite pure enough not to absorb neutrons, which the German programme could not obtain and which sent it down a slower route

is a source for

  • Battery graphite — material · the natural route: flake graphite floated, rounded into potato-shaped particles at a yield of 30 to 50 per cent, purified and coated

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • Crystallography Open Database
    COD Advisory Board / Vilnius University · CC0 — contributors place data in the public domain

Questions this page answers

Where it comes from, and what it becomes

Follow Graphite back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Downstream — what it becomes

  • Graphite → is a source for (the natural route: flake graphite floated, rounded into potato-shaped particles at a yield of 30 to 50 per cent, purified and coated) → Battery graphite → is used in (the anode of essentially every cell ever sold, and roughly twice the mass of the cathode it is paired with) → Lithium-ion cell → is used in (and portable computing came first by two decades) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
  • Graphite → is used in (the anode, unglamorous and the largest component by mass after the cathode) → Lithium-ion cell → is used in (and portable computing came first by two decades) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
  • Graphite → is associated with (reactor-grade graphite pure enough not to absorb neutrons, which the German programme could not obtain and which sent it down a slower route) → The wartime materials programmes complete chain
  • Graphite → is a component of (in magnesia-carbon brick for steel ladles, where the carbon stops the slag wetting the grain and is why the lining survives the pour) → Refractory brick → is an input to (or installed unfired as a monolithic castable and cured by the furnace's own first heat) → Firing → produces (as sintering, from refined powders rather than clay) → Technical ceramic → is used in (the honeycomb monolith the metals are dispersed across, which supplies the surface area and survives the thermal cycling) → Catalytic converter → is used as (the largest catalytic application by metal value there is) → Catalysis
  • Graphite → is a component of (in metamorphosed carbon-rich sediments, and the source of flake graphite — the form batteries and refractories want) → Schist → is a source for (the next step up in grade, where mica is consumed and the minerals separate into bands) → Gneiss
  • Graphite → is used as → Electrical conduction

These are the most distinct paths onward. Graphite ends up in others besides.