metamorphic
Tumbled yellow-brown jasper
Jasper, microcrystalline quartz (SiO₂) with iron-oxide impurities
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque mustard-yellow to brown with diffuse streaking, waxy to dull luster, and no visible cleavage. It is a compact microcrystalline quartz aggregate with specific gravity near 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; opaque mustard-yellow to brown with diffuse streaking, waxy to dull luster, and no visible cleavage. It is a compact microcrystalline quartz aggregate with specific gravity near 2.6.
Formation & geological history
Forms when silica-rich fluids cement or replace sediments and volcanic material, with iron oxides producing the yellow-brown color; its exact geologic age and locality cannot be determined from the photograph.
Uses & applications
Commonly cut and polished for cabochons, beads, worry stones, carvings, and decorative objects; modest commercial value unless unusually patterned or from a notable locality.
Geological facts
Jasper is technically a variety of chalcedony or microcrystalline quartz, though the term is used broadly for opaque silica-rich stones. Yellow coloration commonly reflects limonite or goethite.
Field identification & locations
Identify it by its opaque appearance, smooth waxy polish, dense feel, and inability to scratch easily with a steel blade; a streak test on unglazed ceramic and hardness testing can confirm it. Common sources include Brazil, India, Madagascar, Australia, and the western United States.
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