sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, yellow, or earthy; Luster: Dull to greasy; Crystal Structure: Microcrystalline; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Reddish-brown, yellow, or earthy
- Luster
- Dull to greasy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, yellow, or earthy; Luster: Dull to greasy; Crystal Structure: Microcrystalline; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the accumulation of fine silica-rich sediment or volcanic ash, often influenced by mineral hydrothermal fluids that replace organic matter or rock matrices over millions of years.
Uses & applications
Commonly used in lapidary arts, jewelry (cabochons), aquarium decoration, and historical stone tools (due to its sharpenable fracture).
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning 'spotted stone.' It has been used for seals and amulets since the Indus Valley Civilization.
Field identification & locations
Identify by its waxy to dull luster, lack of transparency (even on thin edges), and inability to be scratched by a steel pocket knife. Commonly found in riverbeds and desert environments.
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