mineral

Polished banded agate (likely purple chalcedony/jasper)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide-rich jasper bands

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent purple, reddish-brown, and gray bands; vitreous to waxy luster; cryptocrystalline quartz with no cleavage; specific gravity about 2.6. The rough outer rind and polished face are characteristic of a cut slab or display specimen.

Identified August 24, 2026More mineral →

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At a glance

Common name: Polished banded agate (likely purple chalcedony/jasper)
Scientific name: Microcrystalline quartz, SiO₂; chalcedony with iron-oxide-rich jasper bands
Category: mineral
Identified: August 24, 2026
Method: Standard

AI Estimated Value

Approximately $20–$100 for a common polished specimen; $100–$300+ for large, vividly colored, unusually translucent, or exceptional display pieces.

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

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony and jasper, commonly with iron staining. Individual agate bands may form over thousands to millions of years; the exact geological age is locality-dependent.

Uses & applications

Used for cabochons, carvings, bookends, decorative slabs, and lapidary objects; valued mainly for attractive banding and translucency.

Geological facts

Purple coloration may result from manganese, iron, or heat treatment, while reddish-brown zones commonly contain hematite or other iron oxides.

Field identification & locations

Identify by curved or parallel concentric banding, waxy quartz appearance, hardness, and inability to scratch with a steel knife easily. Common sources include Brazil, Uruguay, Mexico, Madagascar, and the western United States.