Graphite
Graphite is a soft, grey, greasy-feeling form of pure carbon, C, made of flat hexagonal sheets. It marks paper, conducts electricity, and takes its name from the Greek for 'to write.'
Graphite is a soft, grey, greasy-feeling form of pure carbon, C, made of flat hexagonal sheets. It marks paper, conducts electricity, and takes its name from the Greek for "to write."
🪨 Geology Guide Specimen: Open Graphite in the CRV Science Rock & Mineral ID Guide to log the specimen, compare it with the other 8 mineral classes of Dana / Strunz Classes, and test your eye in LithoClade.
Sheets of Carbon: Why Is Graphite Soft?
Within each sheet, carbon atoms are strongly bonded in a honeycomb pattern, but the sheets are held together by weak forces and slide over one another. The mineral has a hardness of only 1 to 2, a perfect cleavage in one direction and a metallic grey luster. A single sheet is called graphene.
Metamorphic Carbon: Where Does Graphite Form?
Graphite forms when organic carbon in sedimentary rocks is heated during metamorphism, so it is found in marble, schists and gneisses, and in some hydrothermal veins. It is also the end of the coal series that ends with anthracite.
Uses: Pencils to Batteries
Graphite at a Glance
| Property | Value |
|---|---|
| Type / variety | C • Hexagonal Sheet Native Carbon |
| Composition | C (sp²-Hybridized Planar Hexagonal Graphene Sheets) |
| Geology Guide group | Minerals (8 Major Chemical Groups) |
| Mineral Group | Native Elements |
| Mohs hardness | Mohs 1–2 (leaves a dark grey mark on paper) |
| Texture / habit | Flexible hexagonal flakes, foliated masses, or radiating nodules |
| Density | 2.09–2.23 g/cm³ |
| Lustre and cleavage | Metallic steel-grey to black with a greasy feel, perfect basal cleavage, and electrical conductivity |
| Geological setting | High-grade metamorphic marbles, schists, gneisses, and hydrothermal veins |
| Diagnostic feature (Geology Guide) | Steel-grey, greasy-feeling, electrically conductive flaky crystal (Mohs 1–2) that marks paper with a dark streak—despite sharing the exact pure carbon composition of Mohs-10 diamond! |
| Formula | C |
| Hardness | 1 to 2 |
See Also
- Diamond — the hard polymorph of carbon
- Anthracite — the highest-rank coal
- Carbon — the element