mineral

Polished orbicular jasper

Jasper, microcrystalline quartz (SiO₂) with iron-oxide and other mineral inclusions

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Identified August 16, 2026More mineral →

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Physical properties

Opaque, multicolored reddish-brown, gray, cream, and dark green material with a waxy to glassy luster; Mohs hardness 6.5–7, massive microcrystalline structure, no visible cleavage, specific gravity about 2.5–2.9. The foreground piece is a polished/tumbled dark jasper, while the larger specimen appears rough to partly polished.

Formation & geological history

Forms when silica-rich groundwater replaces or fills volcanic sediments and cavities, incorporating iron oxides and other inclusions; generally associated with volcanic environments and may range from Paleozoic to Cenozoic in age.

Uses & applications

Used for cabochons, beads, carvings, ornamental objects, and lapidary displays; durable varieties are occasionally used as decorative stone.

Geological facts

Orbicular or brecciated patterns arise from concentric mineral growth or fragmented material cemented by silica. Red coloration commonly reflects hematite or other iron oxides.

Field identification & locations

Identify by its opaque appearance, fine-grained texture, hardness, and inability to scratch with a steel knife; acid produces no reaction. Common sources include Madagascar, Oregon, Utah, India, and Australia.