metamorphic
Black-and-white jasper
Jasper, microcrystalline quartz (SiO₂), with contrasting white mineral inclusions
AI-generated identification · may be incorrectOpaque, smoothly tumbled, dark brown-black with irregular white patches; vitreous to waxy luster and no visible cleavage. Hardness is about 6.5–7 Mohs; fine-grained quartz mosaic, with specific gravity near 2.6.
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Physical properties
Opaque, smoothly tumbled, dark brown-black with irregular white patches; vitreous to waxy luster and no visible cleavage. Hardness is about 6.5–7 Mohs; fine-grained quartz mosaic, with specific gravity near 2.6.
Formation & geological history
Formed when silica-rich fluids replaced or cemented fine sediments or volcanic material, incorporating pale minerals such as quartz, feldspar, or calcite. Jasper is generally Precambrian to Cenozoic in age and occurs in many volcanic and sedimentary terrains.
Uses & applications
Used for cabochons, beads, carvings, polished stones, and ornamental objects; its durability also suits small decorative applications. Common tumbled pieces usually have modest commercial value.
Geological facts
The pattern is natural brecciation or mineral veining rather than crystal banding, and the exact variety may be marketed as black-and-white jasper or spotted jasper. A drop of dilute hydrochloric acid can fizz if the white material is calcite, but not if it is quartz.
Field identification & locations
Common in volcanic regions and silica-rich sedimentary deposits worldwide, including the western United States, Mexico, India, Madagascar, and Australia. A glassy quartz-like edge, lack of cleavage, and resistance to scratching help distinguish it from softer black limestone.
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