Rock Identifier
Likely graphite-rich ore or galena-bearing rock (Graphite (C) or galena (PbS), identification uncertain from photograph) — mineral
mineral

Likely graphite-rich ore or galena-bearing rock

Graphite (C) or galena (PbS), identification uncertain from photograph

AI-generated identification · may be incorrect

Dark gray to black, strongly metallic-looking, irregular granular mass with reflective cleavage faces. Graphite is very soft (Mohs 1–2), greasy, and marks paper; galena is harder (Mohs 2.5–3), exceptionally dense, and has cubic cleavage.

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Physical properties

Dark gray to black, strongly metallic-looking, irregular granular mass with reflective cleavage faces. Graphite is very soft (Mohs 1–2), greasy, and marks paper; galena is harder (Mohs 2.5–3), exceptionally dense, and has cubic cleavage.

Formation & geological history

Graphite forms through metamorphism of carbon-rich sediments or in igneous veins; galena forms mainly in hydrothermal sulfide veins. A precise age and origin require locality and testing.

Uses & applications

Graphite is used in lubricants, refractories, batteries, and pencils; galena is an important lead ore and may contain silver. Neither is typically used as a gemstone.

Geological facts

A streak test, density measurement, and cleavage examination are highly diagnostic: graphite leaves a black streak and feels greasy, while galena commonly breaks into cubic fragments and feels unusually heavy.

Field identification & locations

Common graphite localities include Sri Lanka, Madagascar, China, and metamorphic terrains worldwide; galena is widespread in hydrothermal mining districts. Do not handle or grind suspected galena without precautions because lead sulfide is toxic.