mineral

Botryoidal chalcedony (gray agate/jasper-like silica)

Microcrystalline quartz, SiO₂; likely chalcedony with opaque quartz or jasper inclusions

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, with a waxy to vitreous luster, gray-white to tan coloration, translucent edges, and curved botryoidal surfaces. It has cryptocrystalline quartz structure, no obvious cleavage, conchoidal fracture, and specific gravity around 2.6.

Identified August 10, 2026More mineral →

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At a glance

Common name: Botryoidal chalcedony (gray agate/jasper-like silica)
Scientific name: Microcrystalline quartz, SiO₂; likely chalcedony with opaque quartz or jasper inclusions
Category: mineral
Identified: August 10, 2026
Method: Standard

AI Estimated Value

About $10–$50 for a common rough or hand specimen; $50–$200+ if unusually large, attractive, well-polished, or strongly patterned.

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, fractures, or vesicles in volcanic rock and precipitates in successive layers. The specimen’s exact geological age cannot be determined from the image; chalcedony occurs from ancient volcanic terrains to modern deposits.

Uses & applications

Used for ornamental stone, carvings, cabochons, beads, and polished display pieces; massive material is also used decoratively in countertops and architectural objects.

Geological facts

Botryoidal means the surface developed as overlapping rounded growths. Gray chalcedony can resemble weathered limestone, opal, or massive quartz, but its conchoidal fracture and hardness help distinguish it.

Field identification & locations

Look for waxy luster, translucent margins, curved banding or growth layers, and resistance to scratching by steel. Common localities include Brazil, Uruguay, Mexico, India, Madagascar, and volcanic regions worldwide.