Rock Identifier
Tumbled brown jasper (Jasper, microcrystalline quartz (SiO₂), commonly with iron-oxide impurities) — mineral
mineral

Tumbled brown jasper

Jasper, microcrystalline quartz (SiO₂), commonly with iron-oxide impurities

AI-generated identification · may be incorrect

Opaque chocolate-brown, smooth and rounded from tumbling, with a dull to waxy luster; Mohs hardness about 6.5–7, no visible cleavage, cryptocrystalline quartz structure, and specific gravity near 2.6.

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Physical properties

Opaque chocolate-brown, smooth and rounded from tumbling, with a dull to waxy luster; Mohs hardness about 6.5–7, no visible cleavage, cryptocrystalline quartz structure, and specific gravity near 2.6.

Formation & geological history

Jasper forms when silica-rich fluids replace or cement volcanic ash, sediment, or fractured rock, with iron oxides producing the brown color. Deposits occur in many ages and regions, including India, Madagascar, Brazil, and the western United States.

Uses & applications

Used as inexpensive ornamental stone, beads, cabochons, carvings, and lapidary material; polished pieces are popular in collections and crafts.

Geological facts

Jasper is technically an opaque variety of chalcedony or microcrystalline quartz. Color and patterns reflect impurities such as hematite, goethite, clay, and other minerals.

Field identification & locations

Identify it by its opaque earthy color, glassy-to-waxy polish, absence of cleavage, and ability to scratch ordinary glass. The pictured piece is likely commercially tumbled rather than naturally rounded.