sedimentary

Black Jasper

Silicon dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Opaque black, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (microcrystalline quartz), Cleavage: None, Specific Gravity: 2.58-2.91

Hardness: 6

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Opaque black, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (microcrystalline quartz), Cleavage: None, Specific Gravity: 2.58-2.91

Formation & geological history

Formed through the deposition of silica-rich fluids within sedimentary or volcanic rock cavities, often containing organic pollutants or iron inclusions that provide its dark pigmentation.

Uses & applications

Commonly used for lapidary work, jewelry (especially men's accessories), tumbled stones for collectors, and historically as a touchstone to test the purity of gold and silver.

Geological facts

Black jasper is also known as Basanite in some contexts. It is one of the most stable forms of quartz and has been used since antiquity to determine the gold content of alloys by observing the streak left on its surface.

Field identification & locations

Identify in the field by its conchoidal fracture, high hardness (cannot be scratched by a steel knife), and dense, opaque black color even when held to a light. Found globally with prominent deposits in India, Russia, and the USA.