mineral

Tumbled chalcedony (likely carnelian or mossy agate)

Microcrystalline quartz, SiO₂; chalcedony variety, possibly iron-stained carnelian

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-brown with reddish-orange inclusions, vitreous to waxy luster, cryptocrystalline structure, and no visible cleavage. Specific gravity is about 2.6.

Identified August 16, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; translucent gray-brown with reddish-orange inclusions, vitreous to waxy luster, cryptocrystalline structure, and no visible cleavage. Specific gravity is about 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, later colored by iron oxides; commonly Cenozoic to older, depending on its host rock.

Uses & applications

Used for beads, cabochons, carvings, and inexpensive ornamental stone; polished tumbles are primarily collectible or decorative.

Geological facts

The smooth rounded shape indicates human tumbling. Brown-red coloration commonly results from hematite or limonite inclusions rather than a separate crystal species.

Field identification & locations

Identify by its waxy luster, translucency, lack of cleavage, and resistance to scratching; quartz should scratch glass, though testing can damage the specimen. Common sources include Brazil, India, Uruguay, Madagascar, and the western United States.