sedimentary
Chert/Jasper
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7, Color: Brown/tan, Luster: Waxy to dull, Crystal structure: Microcrystalline, Cleavage: None (conchoidal fracture). It often has a smooth texture when water-worn.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7, Color: Brown/tan, Luster: Waxy to dull, Crystal structure: Microcrystalline, Cleavage: None (conchoidal fracture). It often has a smooth texture when water-worn.
Formation & geological history
Formed from silica-rich fluids in sedimentary environments or as nodules in limestone/chalk. Often rounded by river or glacial action.
Uses & applications
Historically used for tools (arrowheads, scrapers) due to conchoidal fracture. Some varieties are used in lapidary for polishing or tumbling.
Geological facts
Jasper and chert are essentially the same material (microcrystalline quartz), with 'jasper' often used for more colorful, opaque varieties. The brown color in this specimen is likely due to iron oxide impurities.
Field identification & locations
Identified by its hardness (scratches glass), waxy luster, and conchoidal fracture. Very common in riverbeds and glacial till.
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