sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Brownish-tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7. It is opaque and very smooth to the touch in worn areas.

Hardness: 7 on Mohs scale
Color: Brownish-tan
Luster: Dull to waxy

Identified July 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or by chemical precipitation from silica-rich fluids in sedimentary basins. This specimen appears river-worn or weathered.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp edges when broken. Now used as decorative garden stone, in landscaping, or as a lapidary material for tumbling.

Geological facts

Chert and its variety Jasper have been used by humans for millions of years. Because of its high silica content, it is extremely chemically stable and resistant to weathering.

Field identification & locations

Identify by its conchoidal (shell-like) fracture patterns and the fact that it can scratch glass easily. Look for it in riverbeds, gravel pits, and sedimentary rock outcrops.