sedimentary

Chert (Tan/Buff Chert)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, buff, or cream; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic atoms); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Tan, buff, or cream
Luster: Waxy to dull

Identified April 7, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, buff, or cream; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic atoms); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation from silica-rich fluids in marine or groundwater environments. It typically forms as nodules or bedded layers within limestone or chalk.

Uses & applications

Historically used for making stone tools (arrowheads/scrapers) due to its sharp edges. Modernly used as road aggregate, in glass manufacturing, or as decorative landscaping stone.

Geological facts

Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, leading to its historical use as 'flint' in firearms and fire-starting kits.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its inability to be scratched by a steel knife. It often feels denser and smoother than surrounding limestone.