mineral

Polished banded agate (likely Botswana or plume-type agate)

Microcrystalline quartz, mainly chalcedony (SiO₂), with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; brown, gray, cream, and black curved banding; waxy to vitreous luster when polished; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.6.

Identified August 27, 2026More mineral →

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At a glance

Common name: Polished banded agate (likely Botswana or plume-type agate)
Scientific name: Microcrystalline quartz, mainly chalcedony (SiO₂), with iron-oxide inclusions
Category: mineral
Identified: August 27, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a common polished palm stone; $30–$100+ for unusually vivid banding, translucency, size, or provenance.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Hardness 6.5–7 Mohs; brown, gray, cream, and black curved banding; waxy to vitreous luster when polished; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.6.

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in successive bands. Most specimens formed during Phanerozoic volcanic activity, commonly in cavities of basalt and other lavas.

Uses & applications

Used for cabochons, carvings, bookends, ornaments, and lapidary collections; durable polished agate is also used in jewelry and decorative objects.

Geological facts

The specimen’s rounded shape and glossy surface indicate tumbling or polishing. Band patterns develop from changing chemistry, iron content, and fluid conditions during repeated silica deposition.

Field identification & locations

Identify by translucent edges, curved or concentric bands, waxy polish, and hardness sufficient to scratch ordinary glass; it will not fizz in dilute acid. Common sources include Brazil, Uruguay, Botswana, Mexico, India, and the United States.