sedimentary

Chert (Nodule)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Brown, tan, reddish; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Brown, tan, reddish
Luster: Waxy to dull

Identified March 5, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Brown, tan, reddish; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through a chemical process where silica-rich fluids replace organic material or fill voids in limestone or chalk beds. Often Paleozoic to Mesozoic in age. Found in marine sedimentary environments.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used in construction aggregate, as road surfacing, and occasionally for lapidary work (polishing/tumbling).

Geological facts

Because it breaks with a conchoidal fracture (smooth, curved surfaces), it was the primary material used by prehistoric humans to create sharp cutting tools and weapons.

Field identification & locations

Identify by its 'waxy' appearance and smooth, glass-like fracture surfaces when chipped. Commonly found in gravel beds or eroding out of limestone outcrops worldwide. Collectors look for unique banding or color patterns.