mineral
Tumbled carnelian agate
Microcrystalline quartz (chalcedony), SiO₂; iron-oxide colored
AI-generated identification · may be incorrectTypically reddish-brown, orange, and translucent to opaque with a waxy-to-glassy luster and no visible cleavage; Mohs hardness 6.5–7, trigonal quartz structure, specific gravity about 2.6. The rounded, glossy shape indicates mechanical tumbling and polishing.
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Physical properties
Typically reddish-brown, orange, and translucent to opaque with a waxy-to-glassy luster and no visible cleavage; Mohs hardness 6.5–7, trigonal quartz structure, specific gravity about 2.6. The rounded, glossy shape indicates mechanical tumbling and polishing.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, with iron oxides producing red and brown colors; commonly Paleozoic–Cenozoic, though ages vary by deposit. This specimen is a polished human-processed geological material.
Uses & applications
Used for inexpensive jewelry, beads, carvings, cabochons, ornaments, and lapidary practice; it has little construction use as a small specimen.
Geological facts
Carnelian is the orange-red variety of chalcedony, while banded material is commonly called agate. Heating can intensify or alter its red-orange coloration.
Field identification & locations
Identify by hardness, waxy luster, red-orange coloration, translucency at thin edges, and lack of cleavage; common sources include Brazil, India, Uruguay, Madagascar, and the United States. It should not scratch easily with a steel knife, though testing can damage polish.
