sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (cannot be scratched by steel); Color: Brown with white inclusions; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Brown with white inclusions
Luster: Dull to waxy

Identified June 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via the accumulation of silica-rich organic remains or chemical precipitation within sedimentary layers. This water-worn pebble likely dates from common sedimentary cycles ranging from the Paleozoic to Cenozoic eras.

Uses & applications

Historically used for making stone tools; currently used in landscaping, as tumbling rough for lapidary work, and as decorative gravel.

Geological facts

Chert and Jasper are varieties of microcrystalline quartz. This specific specimen appears to be a stream-tumbled pebble where the rounded shape is the result of mechanical weathering in a river or beach environment.

Field identification & locations

Identify by its hardness (will scratch glass) and smooth, waxy feel when wet. Found globally in riverbanks, glacial tills, and marine deposits. It often shows a characteristic shell-like (conchoidal) fracture when broken.