
sedimentary
Polished brecciated jasper (likely septarian or iron-rich jasper)
Microcrystalline quartz (chalcedony), SiO₂, with iron oxides and possibly calcite or other rock fragments
AI-generated identification · may be incorrectTypically Mohs hardness 6.5–7 for the jasper matrix; opaque, dark brown to black with rusty yellow-brown patches and a glassy-to-waxy polish. Massive cryptocrystalline quartz lacks visible cleavage; specific gravity is about 2.5–2.7.
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Physical properties
Typically Mohs hardness 6.5–7 for the jasper matrix; opaque, dark brown to black with rusty yellow-brown patches and a glassy-to-waxy polish. Massive cryptocrystalline quartz lacks visible cleavage; specific gravity is about 2.5–2.7.
Formation & geological history
Forms when silica-rich fluids cement fine sediment or breccia fragments, with iron producing the brown coloration; some varieties develop from altered volcanic or sedimentary material. Formation ages vary widely, commonly from Paleozoic to Cenozoic deposits.
Uses & applications
Used as a decorative stone, cabochon, tumbled stone, paperweight, and inexpensive jewelry material; polished pieces are primarily valued for appearance.
Geological facts
Jasper is an opaque variety of chalcedony, and its patterns commonly reflect mineral staining, brecciation, or replacement rather than large crystals.
Field identification & locations
Identify it by its opaque body, fine-grained texture, strong polish, and inability to scratch with a steel knife; quartz will scratch glass, though this test can damage the specimen. Common sources include Brazil, Madagascar, India, Mexico, and the western United States.
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