mineral

Polished brown chalcedony (likely carnelian or sard)

Chalcedony, microcrystalline quartz (SiO₂); brown varieties are commonly termed sard, while reddish-orange material is carnelian

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; smooth vitreous-to-waxy luster, brown translucent body, cryptocrystalline quartz with no visible cleavage. The rounded shape and gloss indicate tumbling/polishing.

Identified August 30, 2026More mineral →

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At a glance

Common name: Polished brown chalcedony (likely carnelian or sard)
Scientific name: Chalcedony, microcrystalline quartz (SiO₂); brown varieties are commonly termed sard, while reddish-orange material is carnelian
Category: mineral
Identified: August 30, 2026
Method: Standard

AI Estimated Value

$2–$15 for a small common tumbled stone; $20–$75 for an attractive larger or unusually translucent cabochon.

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

Hardness 6.5–7 Mohs; smooth vitreous-to-waxy luster, brown translucent body, cryptocrystalline quartz with no visible cleavage. The rounded shape and gloss indicate tumbling/polishing.

Formation & geological history

Forms when silica-rich groundwater deposits microcrystalline quartz in cavities and fractures, often in volcanic rocks; commonly Cenozoic to older, with age dependent on host rock.

Uses & applications

Used for cabochons, beads, carvings, paperweights, and inexpensive ornamental stones; valued more for color and pattern than rarity.

Geological facts

Chalcedony’s color can result from iron oxides; heating may intensify reddish tones. Exact identification as sard versus carnelian requires observing color and translucency under strong light.

Field identification & locations

Common sources include India, Brazil, Uruguay, Madagascar, Australia, and the United States. Field clues are waxy luster, conchoidal fracture, lack of cleavage, and ability to scratch glass; the image alone cannot exclude brown jasper or dyed agate.