sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Pinkish-tan to light purple, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Pinkish-tan to light purple, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation of silica in groundwater or marine environments, often replacing original limestone structure.
Uses & applications
Historically used for stone tools and weapons due to conchoidal fracture; currently used for lapidary work, tumbling, and as decorative gravel.
Geological facts
Because of its sharpness when broken, it was the primary material for arrowheads and scrapers for thousands of years. This specific specimen shows a light purplish hue common in jasper varieties.
Field identification & locations
Identify in the field by its smooth, shell-like fracture pattern (conchoidal), its ability to scratch glass, and its waxy feel. It often has a weathered white 'cortex' or rind on the outer surface.
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