mineral
Tumbled chalcedony or agate
Microcrystalline quartz (SiO₂), likely pale agate/chalcedony
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; cream, tan, and orange-brown translucent coloration with a waxy to vitreous luster. Quartz has a trigonal crystal structure but occurs here as compact microcrystalline material, without visible cleavage; specific gravity is about 2.60–2.65.
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Physical properties
Hardness 6.5–7 Mohs; cream, tan, and orange-brown translucent coloration with a waxy to vitreous luster. Quartz has a trigonal crystal structure but occurs here as compact microcrystalline material, without visible cleavage; specific gravity is about 2.60–2.65.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, precipitating in layers or diffuse bands. The specimen is likely a naturally formed piece subsequently rounded and polished by tumbling; its exact geological age and locality cannot be determined from the image.
Uses & applications
Used for jewelry, cabochons, carvings, decorative objects, and lapidary practice; it has little industrial value as an individual specimen.
Geological facts
Agate is a banded variety of chalcedony, while less visibly banded material is commonly sold as chalcedony or jasper. Orange tones may result from iron oxides.
Field identification & locations
Look for translucency, a smooth waxy surface, hardness sufficient to scratch glass, and curved or diffuse internal banding; common sources include Brazil, Uruguay, Mexico, India, and the western United States.
