sedimentary

Chert (with Quartz Druzy)

Microcrystalline Silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, brown, and grey; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Tan, brown, and grey
Luster: Waxy to vitreous

Identified June 6, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, brown, and grey; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen shows secondary quartz crystallization (druzy) in a vug or cavity.

Uses & applications

Used historically for stone tools due to its conchoidal fracture; currently used in construction aggregate, as a gemstone (jaspers), and as collector specimens.

Geological facts

Chert is one of the most durable sedimentary rocks and often preserves microfossils. High-quality varieties like flint were the primary technological material for early humans.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife), waxy luster, and smooth, curved fracture surfaces. Commonly found in limestone or chalk beds.