mineral
Tumbled jasper or brecciated jasper
Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and dark mineral inclusions
AI-generated identification · may be incorrectOpaque yellow-brown, black-speckled, polished, and waxy to vitreous; quartz hardness about 6.5–7 Mohs, no cleavage, cryptocrystalline structure, and specific gravity around 2.6. The rounded shape indicates tumbling or natural water wear.
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Physical properties
Opaque yellow-brown, black-speckled, polished, and waxy to vitreous; quartz hardness about 6.5–7 Mohs, no cleavage, cryptocrystalline structure, and specific gravity around 2.6. The rounded shape indicates tumbling or natural water wear.
Formation & geological history
Jasper forms when silica-rich groundwater replaces or cements volcanic, sedimentary, or hydrothermal material, with iron oxides producing yellow-brown colors. Deposits occur in many regions and may range from Precambrian to younger geological ages.
Uses & applications
Used for cabochons, beads, carvings, polishing stones, and inexpensive decorative specimens; rarely used as aggregate or ornamental stone.
Geological facts
Jasper is a variety of opaque chalcedony and is valued mainly for pattern and color rather than transparency. The dark patches may represent manganese or iron-bearing inclusions, breccia fragments, or other rock minerals.
Field identification & locations
Identify it by its opacity, fine-grained texture, waxy luster, lack of visible crystal faces, and resistance to scratching glass; a steel file generally scratches it only with difficulty. Common sources include India, Madagascar, Brazil, Mexico, and the western United States.
