sedimentary

Chert (with inclusions)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Cream, grey, and tan with darker patches; Luster: Waxy to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Cream, grey, and tan with darker patches
Luster: Waxy to dull

Identified May 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation from hydrothermal fluids in marine environments. This specimen appears water-worn, likely collected from a riverbed or beach.

Uses & applications

Historically used for stone tools (flintknapping) due to its sharp edges when broken. Today used as decorative gravel, in construction as road base, and by hobbyist collectors.

Geological facts

Chert is so durable that it can survive long periods of erosion, which is why it is often found as smooth pebbles in stream beds. Some cherts contain microscopic fossils. Darker varieties are often called flint.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its smooth, waxy feel and conchoidal (shell-like) fracture patterns. Frequently found in limestone and dolomite formations worldwide.