sedimentary

Chert (Jasper/Agate variant)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish-orange; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brown, tan, reddish-orange
Luster: Waxy to dull

Identified June 21, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish-orange; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed from the accumulation of silica-rich micro-organic remains or chemical precipitation from hydrothermal fluids in sedimentary basins. This specimen appears water-worn.

Uses & applications

Historically used for stone tools/arrowheads; currently used as decorative gravel, in lapidary work (tumbling/polishing), and for jewelry-making.

Geological facts

Chert is so durable that it can survive long-distance transport in rivers and glacial deposits, often outlasting the softer rocks it was originally embedded in.

Field identification & locations

Identify in the field by its waxy texture, extreme hardness (it will scratch glass), and its smooth, shell-like fracture pattern when broken. Commonly found in riverbeds and gravel pits.