Rock Identifier
Polished brecciated jasper (Jasper, an opaque microcrystalline variety of quartz (SiO₂), likely brecciated and iron-oxide-rich) — mineral
mineral

Polished brecciated jasper

Jasper, an opaque microcrystalline variety of quartz (SiO₂), likely brecciated and iron-oxide-rich

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; waxy to vitreous luster; red-brown, gray, cream, and greenish patches with angular breccia-like patterning. Massive cryptocrystalline structure, no visible cleavage, typically specific gravity 2.5–2.7.

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Physical properties

Mohs hardness 6.5–7; waxy to vitreous luster; red-brown, gray, cream, and greenish patches with angular breccia-like patterning. Massive cryptocrystalline structure, no visible cleavage, typically specific gravity 2.5–2.7.

Formation & geological history

Forms when silica-rich fluids replace or cement volcanic sediment and fractured rock, with iron and other minerals producing the colors. Most jasper is Paleozoic to Cenozoic, though age depends on locality.

Uses & applications

Used for cabochons, carvings, beads, tumbled stones, and ornamental objects; occasionally used as decorative facing stone. This specimen is chiefly a collector and lapidary material.

Geological facts

The gray-green areas may contain chlorite, epidote, or altered volcanic material, while red zones commonly reflect hematite. The polished surface reveals contrasting breccia fragments and silica cement.

Field identification & locations

Identify by its opaque appearance, hardness, fine grain, lack of cleavage, and resistance to scratching by a steel knife; it should not show quartz’s transparent crystals. Common sources include Oregon, California, Arizona, India, Madagascar, and Australia.