sedimentary

Chert (specifically River Stone / Jasper variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, and earthy tones with waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 6
Color: Brown, tan, and earthy tones with waxy luster

Identified March 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, and earthy tones with waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from hydrothermal fluids. This specimen appears water-worn, indicating it was shaped by river or stream transport over thousands of years.

Uses & applications

Historically used for stone tools (arrowheads) due to sharp edges; currently used as landscaping gravel, decorative stones, and low-cost lapidary material for tumbling.

Geological facts

Chert is so durable that it can survive long-distance transport in rivers and along beaches where other rocks break down. In antiquity, it was prized alongside flint for its ability to create sparks when struck against steel.

Field identification & locations

Identify in the field by its hardness (it should scratch glass), waxy feel, and smooth curves where it has chipped (conchoidal fracture). It is ubiquitous in riverbeds and gravel pits worldwide.