gemstone

Polished agate nodule

Agate, microcrystalline quartz (SiO₂), likely with chalcedony and iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent cream, gray, and brown banding with a waxy-to-glassy luster. Microcrystalline quartz has no visible cleavage and conchoidal fracture; the specimen appears cut and polished.

Identified September 16, 2026More gemstone →

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At a glance

Common name: Polished agate nodule
Scientific name: Agate, microcrystalline quartz (SiO₂), likely with chalcedony and iron-oxide inclusions
Category: gemstone
Identified: September 16, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a small common polished piece; attractive banding, unusual inclusions, or documented locality may raise it to $50 or more.

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

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in layers, commonly during the Cenozoic or older volcanic episodes. Exact locality cannot be determined from the image.

Uses & applications

Used for cabochons, ornaments, bookends, and lapidary collectibles; it has little industrial value in this small polished form.

Geological facts

The rusty brown areas are likely iron oxides such as hematite or goethite, while the pale translucent material is chalcedony. Agate’s concentric or irregular bands record repeated mineral deposition.

Field identification & locations

Identify by hardness, waxy translucency, curved banding, and resistance to scratching by steel; avoid confusing it with dyed glass or resin. Common sources include Brazil, Uruguay, Mexico, India, and the United States.