mineral

Tumbled chalcedony (likely moss or gray agate)

Microcrystalline quartz, SiO₂; chalcedony/agate variety

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray-green to brown, waxy-to-dull luster, translucent edges, and no visible cleavage. The rounded shape and surface polish indicate tumbling; rusty spots likely iron-oxide staining, with possible quartz or feldspar inclusions.

Identified August 22, 2026More mineral →

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At a glance

Common name: Tumbled chalcedony (likely moss or gray agate)
Scientific name: Microcrystalline quartz, SiO₂; chalcedony/agate variety
Category: mineral
Identified: August 22, 2026
Method: Standard

AI Estimated Value

About $2–$15 as a small common tumbled stone; $20–$75 or more if it has distinctive mossy patterning, strong translucency, or an attractive polished finish.

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, depositing cryptocrystalline quartz in layers or moss-like patterns. Agate deposits range from Paleozoic to Cenozoic, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, ornamental objects, and inexpensive collector specimens; durable enough for decorative stonework but not typically structural construction aggregate.

Geological facts

Chalcedony is quartz whose crystals are too small to see unaided; agate is patterned chalcedony, commonly showing banding or dendritic inclusions.

Field identification & locations

Identify by its very fine texture, waxy appearance, conchoidal fracture, lack of cleavage, and ability to scratch ordinary glass. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States; exact identification requires a specific-gravity or microscopy test.