sedimentary
Jasper
Jasper (Silica-rich microcrystalline Quartz, SiO2 with Fe2O3 impurities)
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, liver-colored; Luster: Dull to greasy; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Reddish-brown, liver-colored
- Luster
- Dull to greasy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, liver-colored; Luster: Dull to greasy; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
Formation & geological history
Formed from silica-rich fluids depositing in holes or cracks of other rocks, or from the accumulation of silica-rich organic material like radiolaria. The red-brown color comes from high iron oxide content. Often found in Precambrian formations.
Uses & applications
Used primarily as a gemstone for lapidary work (jewelry, cabochons, beads), decorative ornaments, and historically for tools and seal stones.
Geological facts
Jasper is mentioned in many ancient texts, including the Bible. The name comes from the Greek 'iaspis', meaning 'spotted stone'. It is an opaque variety of chalcedony.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel knife), smooth waxy texture, and opaque nature (light will not pass through the edges). Commonly found in river beds and beaches where silica minerals collect.
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