mineral

Tumbled agate (likely Botswana or banded agate)

Microcrystalline quartz, SiO₂ (chalcedony with agate banding)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; white, gray, cream, and faint lavender-brown bands; waxy to glassy luster; cryptocrystalline structure; no visible cleavage, conchoidal fracture; specific gravity about 2.6.

Identified August 30, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; white, gray, cream, and faint lavender-brown bands; waxy to glassy luster; cryptocrystalline structure; no visible cleavage, conchoidal fracture; specific gravity about 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in successive bands. Agate commonly formed during the Paleozoic–Cenozoic eras and was later cut and polished here.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and inexpensive collector specimens; durable agate is also used for burnishers and laboratory mortars.

Geological facts

The curved internal bands reflect changing chemistry, temperature, and silica saturation during cavity filling. The surface appears machine-tumbled and polished.

Field identification & locations

Identify by hardness, waxy translucency, curved banding, and resistance to scratching by a steel knife; it should not fizz in dilute acid. Common sources include Brazil, Uruguay, Botswana, Mexico, and the United States.