mineral
Tumbled jasper, likely ocean jasper
Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide and other mineral inclusions
AI-generated identification · may be incorrectOpaque, rounded and polished; mottled red, green, brown, and gray colors with a resinous to vitreous luster. Mohs hardness 6.5–7; no cleavage; cryptocrystalline quartz structure; specific gravity about 2.6.
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Physical properties
Opaque, rounded and polished; mottled red, green, brown, and gray colors with a resinous to vitreous luster. Mohs hardness 6.5–7; no cleavage; cryptocrystalline quartz structure; specific gravity about 2.6.
Formation & geological history
Forms when silica-rich groundwater fills cavities or replaces volcanic rock, with iron and other impurities creating the colors and patterns. Ocean jasper formed mainly in Oligocene–Miocene volcanic environments of Madagascar; ordinary jasper has a broader geological age range.
Uses & applications
Used for beads, cabochons, carvings, ornaments, and inexpensive collectibles; polished pieces are commonly sold as worry stones or tumbled stones.
Geological facts
The image shows a small tumbled specimen, so exact identification is uncertain; the green-red pattern is consistent with jasper or ocean jasper but could include brecciated or other patterned chalcedony.
Field identification & locations
Identify by its opaque microcrystalline appearance, high polish, lack of visible cleavage, and inability to scratch it with a steel knife easily. Common sources include Madagascar, Brazil, India, Indonesia, and the western United States.
