sedimentary

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, earthy red; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Brown, tan, earthy red
Luster: Dull to waxy

Identified April 12, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, earthy red; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation from silica-rich fluids in sedimentary environments. Common in marine or riverbed deposits.

Uses & applications

Historically used for stone tools (flintknapping); currently used for decorative landscaping, lapidary arts (polishing), and as drainage gravel.

Geological facts

Chert and its variety Jasper were essential to prehistoric humans because they break with extremely sharp, glass-like edges, making them ideal for arrowheads and knives.

Field identification & locations

Identify by its hardness (will scratch glass), smooth waxy feel when wet, and lack of visible grains. Common in riverbeds and as pebbles in glacial till.