mineral

Tumbled jasper or quartz-rich chert

Microcrystalline quartz (SiO₂), likely jasper/chert with iron-oxide staining

AI-generated identification · may be incorrect

Opaque tan-brown, cream, and gray stone with a subdued waxy-to-dull luster and rounded tumbled surface. Hardness is approximately 6.5–7 Mohs; quartz has a trigonal crystal structure, but the specimen is microcrystalline and shows no visible cleavage.

Identified August 29, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or fills cavities in volcanic or sedimentary material, with iron oxides producing the brown coloration. Its precise geological age and locality cannot be determined from the photograph.

Uses & applications

Used as a lapidary material for tumbled stones, beads, cabochons, and decorative objects; generally not used structurally.

Geological facts

Jasper and chert are descriptive varieties of cryptocrystalline quartz rather than single minerals. The specimen’s rounded shape and polish indicate human tumbling, while the porous, mottled texture is consistent with jasper or altered chert.

Field identification & locations

Commonly found in silica-rich volcanic terrains, sedimentary beds, and gravel deposits. A glass-scratch test can help confirm quartz hardness, but visual identification cannot reliably distinguish jasper from chert or other quartz-rich rocks.