mineral

Tumbled banded agate (likely carnelian or Botswana agate)

Microcrystalline quartz, SiO₂, chiefly chalcedony with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; rounded and polished, with waxy to glassy luster. Brown, cream, gray, and dark purple-brown curved banding; cryptocrystalline quartz has no visible cleavage and specific gravity around 2.6.

Identified August 22, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony in successive layers; coloration commonly comes from iron and manganese oxides. Individual agate layers may range from Precambrian to Cenozoic in age.

Uses & applications

Used for jewelry, cabochons, carvings, ornaments, and lapidary collections; common tumbled pieces have modest commercial value.

Geological facts

The concentric or curved internal bands are characteristic of agate, while translucency at thin edges helps distinguish it from ordinary jasper.

Field identification & locations

Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the United States. Identify by hardness, waxy polish, translucency, and natural banding; exact variety requires close examination or cutting.