mineral

Polished/tumbled jasper or chalcedony

Microcrystalline quartz (SiO₂), likely brown jasper/chalcedony

AI-generated identification · may be incorrect

Smooth, highly polished brown-gold specimen with cloudy cream banding and patches. Quartz hardness is about 7 Mohs; vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, and typical specific gravity near 2.6. The exact variety cannot be confirmed visually.

Identified September 18, 2026More mineral →

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At a glance

Common name: Polished/tumbled jasper or chalcedony
Scientific name: Microcrystalline quartz (SiO₂), likely brown jasper/chalcedony
Category: mineral
Identified: September 18, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a common polished piece; approximately $30–$100+ if unusually attractive, large, or confirmed as a desirable Brazilian agate/jasper variety.

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 or replaces rock, with iron oxides producing the brown coloration. Such material commonly formed in volcanic or sedimentary environments over geologic timescales; it is likely tumbled or cut and polished rather than naturally shaped.

Uses & applications

Used as ornamental stone, cabochons, jewelry, carvings, and polished collectibles. It is not normally used as a structural construction stone in this form.

Geological facts

The cream-and-brown appearance may also resemble iron-stained agate, petrified wood, or brown calcite, but the smooth opaque-to-translucent texture is most consistent with jasper/chalcedony. A hardness test is useful: quartz should resist scratching by a steel blade.

Field identification & locations

Commonly found as pebbles, cavity fillings, and silica-rich nodules. Brazil, including southeastern Brazil near 20.1°S, 42.0°W, is a plausible source region for varied quartz and jasper materials. Confirm with hardness, streak, translucency, and—if available—specific-gravity testing.