sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, green, and dark brown; Luster: Waxy to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91
- Hardness
- 6
- Color
- Reddish-brown, green, and dark brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, green, and dark brown; Luster: Waxy to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91
Formation & geological history
Formed through the infiltration of silica in volcanic ash or fine sediments. Often associated with volcanic activity or seafloor hydrothermal vents, dating ranging from the Precambrian to recent eras.
Uses & applications
Commonly used as a gemstone for lapidary work, jewelry (beads, cabochons), ornamental or decorative stones, and as a collector's specimen.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Old French word 'jaspre', meaning 'spotted stone'. In ancient times, it was believed to provide protection against evil spirits and snake bites.
Field identification & locations
Identify in the field by its opacity, conchoidal fracture, and inability to be scratched by a steel knife. Frequently found as river-worn pebbles or in volcanic deposits in locations like India, Brazil, and the Western USA.
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