sedimentary

Chert / Jasper

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Variegated brown, reddish-orange, and dark grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Variegated brown, reddish-orange, and dark grey
Luster: Waxy to dull

Identified May 23, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Variegated brown, reddish-orange, and dark grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria) or chemical precipitation from fluids in marine environments. Often found in nodes or beds within limestone and greenstone belts.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used as decorative stones, in landscaping, and sometimes as lapidary material for jewelry cabochons.

Geological facts

This specimen shows a distinct conchoidal fracture pattern and a waxy surface texture characteristic of high-silica rocks. The reddish hues suggest the presence of iron oxide (hematite) impurities.

Field identification & locations

Identify by its ability to scratch glass and its smooth, shell-like fracture surfaces. Frequently found in riverbeds and glacial deposits across North America and Europe.