sedimentary

Chert (Jasper variation)

Chert (Silicate mineral, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Rusty orange/brown, Luster: Waxy to dull, Crystal structure: Microcrystalline (Trigonal), Cleavage: None (conchoïdal fracture), Specific gravity: 2.6-2.7

Hardness: 6

Identified April 8, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Rusty orange/brown, Luster: Waxy to dull, Crystal structure: Microcrystalline (Trigonal), Cleavage: None (conchoïdal fracture), Specific gravity: 2.6-2.7

Formation & geological history

Formed from the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by chemical precipitation in saltwater environments. It commonly forms as nodules or bedded deposits throughout various geological ages.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges. Currently used for lapidary work, jewelry (especially as beads or cabochons), and as a landscaping stone.

Geological facts

Chert was one of the most important raw materials for early humans to create arrowheads and scrapers. The orange-brown variety shown is often colloquially called Jasper when it contains significant iron oxide impurities.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its curved, shell-like (conchoidal) fracture pattern when broken. Commonly found in riverbeds or within limestone formations worldwide.