Graphite

Physical Properties

Hardness: 1-2 (Mohs); Color: Steel gray to black; Luster: Metallic to earthy; Crystal Structure: Hexagonal; Cleavage: Perfect basal; Specific Gravity: 2.09-2.23; Greasy feel and leaves a gray streak on paper.

Formation & Geological History

Formed through the regional metamorphism of carbon-rich sedimentary rocks (shales and coals). This particular specimen from Ceylon (Sri Lanka) likely formed in high-grade metamorphic Precambrian terranes through the fluid-deposition of carbon in vein structures.

Uses & Applications

Used in lubricants, pencil leads (mixed with clay), electrodes for steelmaking, refractory bricks, brake linings, and high-strength composite materials.

Geological Facts

Graphite is one of the softest minerals, yet it shares the exact same chemical composition (carbon) as diamond, which is the hardest natural mineral known. Historically, Sri Lanka (Ceylon) is famous for producing high-purity 'vein' or 'lump' graphite.

Field Identification & Locations

Identify in the field by its extreme softness (can be scratched by a fingernail), metallic luster, ability to write on paper, and distinctive slippery or greasy feel. Found commonly in marble, schist, and gneiss.

Identified on: 4/13/2026

Mode: Standard