Graphite
Graphite (/ˈɡræfaɪt/) is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on a large scale (1.3 million metric tons per year in 2022) for uses in pencils, lubricants, and electrodes. Under high pressures and temperatures it converts to diamond. It is a good (but not excellent) conductor of both heat and electricity.
| Graphite | |
|---|---|
Graphite specimen | |
| General | |
| Category | Native mineral |
| Formula (repeating unit) | C |
| IMA symbol | Gr |
| Strunz classification | 1.CB.05a |
| Crystal system | Hexagonal |
| Crystal class | Dihexagonal dipyramidal (6/mmm) Hermann–Mauguin notation: (6/m 2/m 2/m) |
| Space group | P63mc (buckled) P63/mmc (flat) |
| Unit cell | a = 2.461, c = 6.708 [Å]; Z = 4 |
| Identification | |
| Color | Iron-black to steel-gray; deep blue in transmitted light |
| Crystal habit | Tabular, six-sided foliated masses, granular to compacted masses |
| Twinning | Present |
| Cleavage | Basal – perfect on {0001} |
| Fracture | Flaky, otherwise rough when not on cleavage |
| Tenacity | Flexible non-elastic, sectile |
| Mohs scale hardness | 1–2 |
| Luster | Metallic, earthy |
| Streak | Black |
| Diaphaneity | Opaque, transparent only in extremely thin flakes |
| Specific gravity | 1.9–2.3 |
| Density | 2.09–2.23 g/cm3 |
| Optical properties | Uniaxial (−) |
| Pleochroism | Strong |
| Solubility | Soluble in molten nickel, warm chlorosulfuric acid |
| Other characteristics | strongly anisotropic, conducts electricity, greasy feel, readily marks |
| References | |
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