sedimentary
Black Jasper
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5-7 on Mohs scale; Color: Deep black to charcoal gray; Luster: Dull to vitreous (waxy when polished); Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None; Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Deep black to charcoal gray
- Luster
- Dull to vitreous (waxy when polished)
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Deep black to charcoal gray; Luster: Dull to vitreous (waxy when polished); Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None; Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the deposition of silica-rich sediments or the hydrothermal replacement of organic material and volcanic ash. Often found in association with ancient volcanic activity or marine sedimentary environments.
Uses & applications
Primarily used as a gemstone for jewelry, cabochons, and decorative carvings. In metaphysical circles, it is used as a 'grounding' stone. Historically used for flint-knapping tools.
Geological facts
Also known as 'Basanite' when it is a fine-grained form used as a touchstone for testing the purity of gold and silver. It is an opaque variety of chalcedony.
Field identification & locations
Identify in the field by its smooth, conchoidal fracture, extreme hardness (won't scratch with a knife), and complete opacity even at thin edges. Commonly found in riverbeds or coastal areas as water-worn pebbles.
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