sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, tan, and dark black; Luster: Dull to waxy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Variegated brown, tan, and dark black
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, tan, and dark black; Luster: Dull to waxy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the infiltration of silica-rich fluids into sediment or volcanic ash, often containing iron oxides that provide its color. These specimens can range in age from millions to hundreds of millions of years old.
Uses & applications
Used primarily as decorative lapidary stones, in jewelry making (cabochons), and as a collector's item due to its unique patterns.
Geological facts
Jasper is an opaque variety of chalcedony. The name 'jasper' is derived from the Greek word 'iaspis', meaning 'spotted stone.' It has been used by ancient civilizations for amulets and tools.
Field identification & locations
Identify by its hardness (it will scratch glass), lack of transparency, and smooth, water-worn texture if found near rivers. Often found in gravel beds or mountain regions where silica-rich rocks have weathered.
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