sedimentary
Chert / Jasper
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 (Mohs scale), Color: Variegated brown, reddish-orange, and dark grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Variegated brown, reddish-orange, and dark grey
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Variegated brown, reddish-orange, and dark grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria) or chemical precipitation from fluids in marine environments. Often found in nodes or beds within limestone and greenstone belts.
Uses & applications
Historically used for stone tools (arrowheads). Modernly used as decorative stones, in landscaping, and sometimes as lapidary material for jewelry cabochons.
Geological facts
This specimen shows a distinct conchoidal fracture pattern and a waxy surface texture characteristic of high-silica rocks. The reddish hues suggest the presence of iron oxide (hematite) impurities.
Field identification & locations
Identify by its ability to scratch glass and its smooth, shell-like fracture surfaces. Frequently found in riverbeds and glacial deposits across North America and Europe.
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