sedimentary

Iron-rich chert or jasper

Microcrystalline quartz (SiO₂), colored by iron oxides/hydroxides

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; reddish-brown with dark gray to black areas, dull to waxy luster, and a dense, fine-grained texture. It lacks visible cleavage and commonly breaks with a conchoidal fracture; the image is too limited for a definitive identification.

Identified September 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich sediment or volcanic material becomes silicified, with iron producing the red-brown coloration. Such rocks range from Precambrian to recent geological ages and occur in sedimentary basins and hydrothermal environments.

Uses & applications

Used as decorative stone, tumbled material, lapidary cabochons, and occasionally aggregate; attractive pieces have modest collector value.

Geological facts

Jasper is an opaque variety of chert, whereas chert is generally classified by its microcrystalline quartz composition rather than color.

Field identification & locations

Look for a glassy or waxy surface, very fine grain, conchoidal fracture, and inability to scratch it with a steel knife; streak and acid tests can help distinguish it from ironstone or slag. Common worldwide, including India, Australia, Brazil, and the United States.