sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan, yellow, and black patterns, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline/cryptocrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.58-2.91
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan, yellow, and black patterns, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline/cryptocrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.58-2.91
Formation & geological history
Formed from silica-rich fluids depositing in cracks and voids within volcanic or sedimentary rocks. The colors are derived from iron oxides or other mineral impurities during the crystallization process.
Uses & applications
Commonly used as a gemstone for jewelry, cabochons, decorative carvings, and as a popular specimen for rock tumbling and collection.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning 'spotted stone'. It was one of the favorite gemstones in the ancient world, often appearing in biblical and historical texts.
Field identification & locations
Identify in the field by its hardness (will scratch glass), opaque nature, and smooth conchoidal fractures. Commonly found in riverbeds, desert regions, and volcanic deposits across the Western United States and India.
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