metamorphic
Tumbled yellow jasper
Microcrystalline quartz (chalcedony), SiO₂, colored by iron oxides
AI-generated identification · may be incorrectHardness approximately 6.5–7 Mohs; opaque cream, ochre, and rusty yellow with a fine-grained texture, dull-to-waxy luster, and no visible cleavage. The rounded surface indicates human tumbling and polishing.
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Physical properties
Hardness approximately 6.5–7 Mohs; opaque cream, ochre, and rusty yellow with a fine-grained texture, dull-to-waxy luster, and no visible cleavage. The rounded surface indicates human tumbling and polishing.
Formation & geological history
Jasper forms when silica-rich fluids replace or cement volcanic ash, sediments, or weathered rock; iron oxides create the yellow-brown coloration. Its age depends on the source deposit, commonly ranging from Precambrian to younger volcanic or sedimentary settings.
Uses & applications
Used for inexpensive cabochons, beads, carvings, polished stones, and decorative objects; it has minor industrial value compared with ordinary quartz.
Geological facts
Jasper is technically an opaque variety of chalcedony or microcrystalline quartz, though commercial names often include many similar iron-stained rocks.
Field identification & locations
Identify it by its opaque, fine-grained appearance, waxy polish, strong resistance to scratching, and lack of cleavage; common sources include India, Madagascar, Brazil, South Africa, and the western United States. A definitive identification may require a scratch, streak, or laboratory test.
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