sedimentary

Chert with Quartz Veins

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Dark grey/black with white/cream veins; Luster: Waxy to dull (rock) and vitreous (veins); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Dark grey/black with white/cream veins
Luster: Waxy to dull (rock) and vitreous (veins)

Identified June 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, followed by tectonic stresses that created cracks subsequently filled by hydrothermal quartz.

Uses & applications

Historically used for stone tools due to sharp edges; currently used for decorative stones, landscaping, and lapidary practice.

Geological facts

Chert is so durable that it often survives as smooth river pebbles long after the surrounding bedrock has eroded away. The white lines are 'healed' fractures where mineral-rich water deposited new quartz.

Field identification & locations

Identified by its waxy texture, extreme hardness (scratches glass), and distinctive vein patterns. Common in riverbeds, glacial tills, and coastal areas.