mineral

Tumbled blue-gray chalcedony (likely common agate/chalcedony)

Microcrystalline quartz, SiO₂ (chalcedony; possibly pale blue agate)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; bluish-gray, translucent to opaque, with waxy-to-dull luster and conchoidal fracture. The rounded shape indicates tumbling or natural water wear; no obvious cleavage or crystal faces are visible.

Identified September 13, 2026More mineral →

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At a glance

Common name: Tumbled blue-gray chalcedony (likely common agate/chalcedony)
Scientific name: Microcrystalline quartz, SiO₂ (chalcedony; possibly pale blue agate)
Category: mineral
Identified: September 13, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 for a small tumbled piece; up to roughly $20–$50 if strongly translucent, attractively patterned, or confirmed as quality agate.

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 and fractures in volcanic rocks, commonly during the Cenozoic or older volcanic episodes. Slow deposition produces cryptocrystalline quartz and occasional faint banding.

Uses & applications

Used as an inexpensive ornamental stone, cabochon, bead, carving material, and collector specimen; it has little industrial value in this small form.

Geological facts

Chalcedony is an aggregate of microscopic quartz varieties, often including fibrous moganite. Its blue-gray color may result from microscopic inclusions, weathering, or subtle treatment.

Field identification & locations

Identify by its glass-scratching hardness, smooth waxy appearance, translucency at thin edges, and lack of visible grains; a steel blade generally will not scratch it. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.