mineral
Tumbled jasper and agate assortment
Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and other mineral impurities
AI-generated identification · may be incorrectOpaque to translucent polished pebbles in red, mauve, pink, brown, and cream; waxy to glassy luster, cryptocrystalline structure, no visible cleavage, Mohs hardness about 6.5–7, specific gravity approximately 2.58–2.65. The patterned brown-and-white pieces may be brecciated or orbicular jasper/agate.
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Physical properties
Opaque to translucent polished pebbles in red, mauve, pink, brown, and cream; waxy to glassy luster, cryptocrystalline structure, no visible cleavage, Mohs hardness about 6.5–7, specific gravity approximately 2.58–2.65. The patterned brown-and-white pieces may be brecciated or orbicular jasper/agate.
Formation & geological history
Silica-rich groundwater filled cavities and fractures in volcanic or sedimentary rocks, later incorporating iron oxides and other inclusions; commonly Paleozoic to Cenozoic, though ages vary by deposit.
Uses & applications
Used for cabochons, beads, carvings, tumbling, decorative objects, and low-cost jewelry; larger jasper is occasionally used as ornamental stone.
Geological facts
Jasper is the opaque variety of chalcedony, while agate is typically banded or translucent. Tumbled surfaces obscure natural textures but reveal color patterns and fine silica polish.
Field identification & locations
Identify by testing for glass-scratching hardness, waxy luster, and lack of cleavage; jasper is generally opaque and agate more translucent or banded. Common sources include Oregon, Idaho, California, Brazil, India, Madagascar, and Australia.
