sedimentary

Weathered jasper (iron-stained chert)

Microcrystalline quartz/chalcedony, SiO₂, with iron-oxide impurities

AI-generated identification · may be incorrect

Typically hardness 6.5–7, opaque, with a dull to slightly waxy luster and conchoidal fracture; this specimen is tan, gray, reddish-brown, and mottled from iron staining. It appears rounded and water-worn, with no visible cleavage.

Identified September 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Jasper forms when silica-rich fluids replace or cement fine sediment, volcanic ash, or hydrothermal material; iron oxides create the red-brown coloration. Formation ages vary widely, commonly Precambrian to younger, followed by prolonged weathering and transport.

Uses & applications

Used as an ornamental and lapidary stone for cabochons, carvings, beads, and polished slices; massive ordinary pieces have little industrial use.

Geological facts

Jasper is a variety of opaque chalcedony or microcrystalline quartz, and color patterns can resemble landscapes or breccia. The pictured pebble may also be iron-stained chert, which can be difficult to distinguish without a fresh break or testing.

Field identification & locations

Identify it by its opaque silica-rich body, hardness sufficient to scratch glass, waxy surface, and conchoidal fracture; common in river gravels and silica-rich volcanic or sedimentary regions worldwide. A streak test should be white, unlike many softer iron minerals.