sedimentary

Red chert (likely jasper-bearing chert)

Microcrystalline quartz (SiO₂), with iron-oxide hematite/goethite impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque reddish-brown to gray, waxy to dull luster, very fine-grained and massive, with no visible cleavage. It commonly breaks with smooth to conchoidal fractures and may show white quartz veining.

Identified September 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica precipitates or replaces sediment, often from marine microscopic organisms; red coloration comes from oxidized iron. Individual specimens may range from Paleozoic to Cenozoic depending on the host formation.

Uses & applications

Used historically for sharp-edged tools and occasionally as aggregate, decorative stone, or lapidary material; attractive pieces may be polished as cabochons or display specimens.

Geological facts

Jasper is an opaque, iron-rich variety of chert; the boundary between ordinary red chert and jasper is gradual. The dark outer rind may represent weathering or a silica-rich cortex.

Field identification & locations

Identify by its glassy/waxy appearance, exceptional hardness, lack of layering or cleavage, and conchoidal fracture; it should scratch window glass. Common in sedimentary terrains, gravel beds, and glacial deposits worldwide.