mineral

Tumbled yellow chalcedony (likely yellow agate or common opal)

Microcrystalline quartz, SiO₂ (chalcedony/agate); exact identification requires testing

AI-generated identification · may be incorrect

Honey-yellow to cream, translucent, waxy-to-glassy luster, curved fracture, and no visible cleavage; chalcedony hardness is about 6.5–7 Mohs, while common opal is 5.5–6.5. The polished surface and rounded shape indicate human tumbling.

Identified September 15, 2026More mineral →

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At a glance

Common name: Tumbled yellow chalcedony (likely yellow agate or common opal)
Scientific name: Microcrystalline quartz, SiO₂ (chalcedony/agate); exact identification requires testing
Category: mineral
Identified: September 15, 2026
Method: Standard

AI Estimated Value

About $2–$15 for a common tumbled stone; $20–$100+ if naturally colored, unusually translucent, or confirmed as fine-quality agate/opal.

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

Chalcedony forms when silica-rich groundwater fills cavities and fractures, often in volcanic rocks; agate develops from successive silica deposition. Common opal forms from hydrated silica gel; formation ages range from recent to ancient depending on the host rock.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and lapidary practice; attractive translucent pieces have modest jewelry value.

Geological facts

The specimen may be dyed or heat-treated, though its warm color can also be natural. A refractive-index, specific-gravity, and water-absorption test can distinguish chalcedony from opal.

Field identification & locations

Common sources include Brazil, Uruguay, Mexico, Madagascar, Australia, and the western United States. Field clues are translucency, waxy luster, conchoidal fracture, and absence of cleavage; a scratch test should be done inconspicuously.