sedimentary

Chert (Jasper)

Sedimentary Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish-orange; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Brown, tan, reddish-orange
Luster: Waxy to dull

Identified July 5, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish-orange; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids. This specimen appears water-worn, suggesting it was transported by a river or stream.

Uses & applications

Historically used for stone tools (flintknapping); currently used in landscaping, as aquarium decor, or polished for lapidary art and jewelry.

Geological facts

Chert is so hard it can scratch steel and was used by prehistoric humans to create sharp spearheads and knives due to its predictable conchoidal fracturing.

Field identification & locations

Identify in the field by its smooth, waxy feel, conchoidal (shell-like) fractures, and its ability to scratch glass. Commonly found in riverbeds or as nodules within limestone.