sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7.0 (Mohs scale); Color: Red, brown, and yellow mottling; Luster: Dull to greasy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Red, brown, and yellow mottling
- Luster
- Dull to greasy
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Red, brown, and yellow mottling; Luster: Dull to greasy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed from the deposition of silica from water or volcanic ash, often associated with iron impurities that give it its reddish-brown color. Found in sedimentary deposits or as nodules in volcanic rocks.
Uses & applications
Used primarily in lapidary work for cabochons, beads, and carvings. Historically used for ornaments and seals.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Old French word 'jaspre', meaning spotted or speckled stone. It is a common material used in ancient lithic tools due to its conchoidal fracture.
Field identification & locations
Identify by its hardness (will scratch glass), opaque nature, and smooth, curved fracture surfaces. Commonly found in riverbeds and desert environments globally, including the Western USA and India.
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