mineral
Tumbled jasper (likely brecciated or orbicular jasper)
Microcrystalline quartz/chalcedony, SiO₂, with iron-oxide inclusions
AI-generated identification · may be incorrectOpaque, polished/tumbled pebble with brown, cream, reddish, and gray patches; vitreous to waxy luster; quartz hardness about 6.5–7 Mohs; no visible cleavage and conchoidal fracture. Exact variety is uncertain from the photograph.
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Physical properties
Opaque, polished/tumbled pebble with brown, cream, reddish, and gray patches; vitreous to waxy luster; quartz hardness about 6.5–7 Mohs; no visible cleavage and conchoidal fracture. Exact variety is uncertain from the photograph.
Formation & geological history
Forms when silica-rich groundwater fills cavities or replaces volcanic sediment, with iron oxides producing red-brown coloration; commonly associated with volcanic rocks, generally formed from Cenozoic to older deposits.
Uses & applications
Used for cabochons, beads, carvings, ornamental objects, and inexpensive lapidary specimens; durability makes it suitable for tumbling.
Geological facts
Jasper is an opaque variety of chalcedony, unlike translucent agate. Red and brown colors typically reflect hematite or limonite impurities.
Field identification & locations
Identify by opacity, waxy polish, mottled patterns, and lack of cleavage; a steel file should not easily scratch it, while quartz will scratch glass. Common sources include Oregon, Idaho, Utah, Madagascar, Brazil, and Australia.
