sedimentary
Chert (Jasper variation)
Chert (Cryptocrystalline microcrystalline Silicon Dioxide, SiO2)
Hardness: 6.5-7 Mohs scale; Color: Red-brown center with olive-green exterior; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Red-brown center with olive-green exterior
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs scale; Color: Red-brown center with olive-green exterior; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich organisms on the ocean floor or through chemical precipitation. The silica replaces organic or carbonate material over millions of years.
Uses & applications
Historically used for stone tools and arrowheads; currently used in jewelry (as jasper), lapidary art, and aquarium decor.
Geological facts
Chert which is red or brown due to iron oxide inclusions is often called jasper. It was one of the most important minerals for early humans due to its ability to hold a sharp edge when fractured.
Field identification & locations
Identify in the field by its waxy texture, smooth conchoidal fracture (looks like glass break patterns), and high hardness (it will scratch glass). Often found in riverbeds or as nodules within limestone.
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