sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, dusky pink; Luster: Waxy to dull; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown, dusky pink
Luster: Waxy to dull

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, dusky pink; Luster: Waxy to dull; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed via the accumulation of silica-rich organic remains (like radiolarians) or the chemical precipitation of silica in sedimentary environments. Common in marine limestone or as nodules in volcanic rocks.

Uses & applications

Historically used for stone tools and lapidary work. Currently used as an ornamental stone, in landscaping, and as a low-cost gemstone for jewelry.

Geological facts

Chert has been used by humans for thousands of years to create arrowheads and scrapers due to its conchoidal fracture which creates sharp edges. Jasper is the opaque, often red/pink variety of chert.

Field identification & locations

Identify by its waxy luster, hardness (it can scratch glass), and its tendency to break into smooth, curved surfaces. Frequently found in riverbeds or as nodules eroding out of limestone bluffs.