sedimentary

Chert

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, tan, white with banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray, tan, white with banding
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, tan, white with banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Gravity: 2.65

Formation & geological history

Forms primarily as nodules or layers in limestone or chalk through the accumulation of silica-rich organic remains like sponges or radiolarians, often during the Paleozoic or Mesozoic eras.

Uses & applications

Historically used for stone tools (arrowheads); currently used in road construction, landscaping, and as a component in glass making.

Geological facts

The banding seen here represents episodic deposition of silica. Chert is so hard it can strike sparks against steel, making it a primary flint material.

Field identification & locations

Identify by its hardness (scratches glass), waxy feel, and sharp shell-like (conchoidal) edges when broken. Commonly found in stream beds or limestone outcrops.