sedimentary

Chert (Common Opal/Jasper mix)

Silicon Dioxide (SiO2) with impurities

AI-generated identification · may be incorrect

Hardness: 6.5-7. Color: Multi-colored (green, tan, brown). Luster: Waxy to resinous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Multi-colored (green, tan, brown)
Luster: Waxy to resinous

Identified July 8, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7. Color: Multi-colored (green, tan, brown). Luster: Waxy to resinous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Formation & geological history

Formed through the accumulation of silica-rich fluids in sedimentary basins or volcanic ash beds, often replacing organic or volcanic material over millions of years.

Uses & applications

Lapidary work for cabochons, knapping for primitive tools/arrowheads, and used in landscaping or as collector rough.

Geological facts

The specimen exhibits a classic conchoidal (shell-like) fracture pattern common in silica rocks, which was historically utilized by early humans to make sharp tools.

Field identification & locations

Look for a glassy or waxy texture and sharp, curved edges where broken. Commonly found in river beds or areas with exposed sedimentary or old volcanic strata.