mineral
Polished jasper slab
Jasper, an opaque microcrystalline variety of chalcedony (SiO₂), colored mainly by iron oxides
AI-generated identification · may be incorrectTypically Mohs 6.5–7; mustard yellow, brown, black, and gray with opaque earthy patterns, waxy-to-vitreous luster, and no visible cleavage. The specimen appears sawn and polished, with a natural rough rind and fractures.
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Physical properties
Typically Mohs 6.5–7; mustard yellow, brown, black, and gray with opaque earthy patterns, waxy-to-vitreous luster, and no visible cleavage. The specimen appears sawn and polished, with a natural rough rind and fractures.
Formation & geological history
Forms when silica-rich groundwater replaces or fills cavities and fractures in volcanic or sedimentary host rock; iron and manganese oxides create the colors. Jasper deposits range from Precambrian to recent, depending on locality.
Uses & applications
Used for cabochons, beads, carvings, decorative slabs, and lapidary collections; durable enough for small ornamental objects but not usually major construction stone.
Geological facts
Jasper is technically a rock dominated by microcrystalline quartz rather than a single pure mineral. Its intricate patterns are produced by brecciation, replacement, fluid flow, and staining.
Field identification & locations
Identify it by its opacity, fine grain, conchoidal fracture, hardness, and resistance to scratching by steel; it should not fizz in dilute acid. Common sources include India, Madagascar, Brazil, the United States, and Australia.
