sedimentary

Black Jasper

Silicon Dioxide (SiO2) with inclusions

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Jet black to dark charcoal, Luster: Vitreous to sub-vitreous, Crystal structure: Hexagonal (Microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6 - 2.9

Hardness: 6

Identified March 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from silica-rich fluids depositing in sedimentary or volcanic environments. The black color usually results from organic impurities (bitumen) or iron sulfides trapped within the microcrystalline quartz structure.

Uses & applications

Primarily used for lapidary work, jewelry (beads and cabochons), metaphysical practice, and as a 'touchstone' for testing the purity of gold.

Geological facts

Black Jasper, specifically known as 'Basanite' when used for testing gold, has been used since ancient times. It remains functionally useful because when gold is rubbed on its surface, the streak's reaction to acid can determine the gold's karat value.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its smooth, waxy luster when tumbled. It is commonly found in riverbeds and coastal regions of the US (Oregon, California), Russia, and India.