Graphite

Hardness: 1-2 (Mohs); Color: Dark gray to black, often with a metallic sheen; Luster: Metallic to dull; Crystal structure: Hexagonal, often found in flaky or tabular forms, massive, or earthy; Cleavage: Perfect basal cleavage; Specific Gravity: 2.09-2.23. It is very soft, greasy to the touch, and leaves a dark mark (streak).

Formed from the metamorphism of carbon-rich sedimentary rocks (like coal or organic shales) under high temperature and pressure. Can also occur in igneous rocks, pegmatites, and hydrothermal veins. Geological age varies depending on the metamorphic event, ranging from Precambrian to relatively recent.

A major component in 'lead' pencils, lubricants (due to its low friction properties), electrodes, refractories, batteries (especially lithium-ion batteries), and as a moderator in nuclear reactors. High purity graphite is used in aerospace and sporting goods.

Allotropes of carbon include graphite, diamond, and fullerene. Graphite is the most stable form of carbon under standard conditions. Its unique layered structure allows for its excellent lubricating properties and electrical conductivity. It is one of the softest minerals.

Identify in the field by its very soft nature (scratches easily with a fingernail), greasy feel, dark gray to black color, metallic luster, and its ability to leave a dark mark (streak) on surfaces. Often found in metamorphic rocks like schist and marble, and in some igneous rocks. Common locations include China, India, Brazil, Canada, and Madagascar. Collectors often seek well-formed crystalline graphite samples or those displaying its distinct flaky habit.