sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brownish-red to tan; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Hardness: 6
Color: Brownish-red to tan
Luster: Waxy to dull

Identified May 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brownish-red to tan; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation from silica-rich fluids within sedimentary rock layers. This specimen shows water-worn rounding, suggesting transport in a river or stream.

Uses & applications

Used historically for stone tools and arrowheads due to its conchoidal fracture. Today used as an ornamental stone, in jewelry (cabochons), and as a landscaping material.

Geological facts

Chert is so hard it can strike sparks against steel. Jasper is the opaque, iron-stained variety of chert. It has been used by humans for over a million years for toolmaking.

Field identification & locations

Identify by its waxy luster, extreme hardness (it will scratch glass), and smooth, curved (conchoidal) break patterns. Commonly found in riverbeds, gravel pits, and sedimentary outcrops worldwide.