sedimentary

Chert (Jasper/Mudstone)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, reddish-brown. Luster: Dull to waxy. Structure: Microcrystalline with conchoidal fracture. Cleavage: None. Specific gravity: 2.6-2.7.

Hardness: 6
Color: Brown, tan, reddish-brown
Luster: Dull to waxy

Identified June 22, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, reddish-brown. Luster: Dull to waxy. Structure: Microcrystalline with conchoidal fracture. Cleavage: None. Specific gravity: 2.6-2.7.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. These rocks can range from hundreds of millions of years in age.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges. Currently used as road aggregate, in jewelry (as jasper), and as a collector's specimen.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture allows it to be shaped into razor-sharp blades, arrowheads, and scrapers.

Field identification & locations

Identify by its extreme hardness (scratches glass), waxy luster on fresh surfaces, and the way it breaks in curved 'shell-like' patterns. Commonly found in limestone beds.