sedimentary

Chert (Jasper/Quartzite variant)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Gray, tan, with reddish-brown iron oxide banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Gray, tan, with reddish-brown iron oxide banding
Luster: Waxy to dull

Identified July 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Gray, tan, with reddish-brown iron oxide banding; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation within sedimentary layers, then smoothed by water erosion through river or glacial transport.

Uses & applications

Historically used for stone tools due to its sharp edges; currently used for landscaping, road aggregate, and as a common tumbling rock for hobbyists.

Geological facts

Chert was one of the most important minerals for early humans, used for making arrowheads and scraping tools because it breaks with incredibly sharp, predictable edges.

Field identification & locations

Commonly found in riverbeds, beaches, and glacial till. Identify in the field by its hardness (will scratch glass) and its smooth, rounded appearance when found as a river stone.