metamorphic
Polished brecciated jasper
Jasper (microcrystalline quartz, SiO₂), likely brecciated and iron-stained
AI-generated identification · may be incorrectOpaque brown, black, cream, and reddish material with a polished vitreous-to-waxy luster; hardness about 6.5–7 Mohs, no cleavage, cryptocrystalline quartz structure, and specific gravity around 2.6–2.7.
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Physical properties
Opaque brown, black, cream, and reddish material with a polished vitreous-to-waxy luster; hardness about 6.5–7 Mohs, no cleavage, cryptocrystalline quartz structure, and specific gravity around 2.6–2.7.
Formation & geological history
Jasper forms when silica-rich fluids replace or cement sediments and volcanic material; brecciated varieties contain angular fragments healed by chalcedony or quartz. Its exact geological age cannot be determined from the photograph and depends on locality.
Uses & applications
Commonly cut into cabochons, beads, tumbled stones, carvings, and ornamental objects; valued mainly as an inexpensive lapidary and collector material.
Geological facts
The contrasting patches are likely angular rock fragments and iron-oxide staining rather than distinct large crystals. Jasper is technically a variety of opaque chalcedony or microcrystalline quartz.
Field identification & locations
Identify it by its opaque appearance, intricate mottled or brecciated pattern, glassy polish, and resistance to scratching; it should scratch ordinary glass but not be scratched by a steel knife. Common sources include India, Madagascar, Brazil, Australia, and the western United States.
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