sedimentary

Chert / River Jasper

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Brown, tan, and cream; Luster: Waxy to sub-vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Brown, tan, and cream
Luster: Waxy to sub-vitreous

Identified March 28, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Brown, tan, and cream; Luster: Waxy to sub-vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary rock layers, often found as nodules or pebbles that have been water-worn over millions of years (commonly Paleozoic to Cenozoic eras).

Uses & applications

Commonly used for lapidary work (tumbling and cabochon making), decorative landscaping, and historically for stone tools due to its sharp edges when broken.

Geological facts

Because of its high hardness and brittle nature, prehistoric humans used this material to create arrowheads and scrapers. It is essentially the same mineral as flint, though 'chert' is the broader geological term.

Field identification & locations

Identify in the field by its waxy appearance, extreme hardness (it will scratch glass), and rounded, water-worn edges if found in riverbeds. It is common in gravel pits and along shorelines globally.