gemstone

Polished chalcedony (likely sagenite or included agate)

Microcrystalline quartz, SiO₂, with iron-oxide and possibly rutile/goethite inclusions

AI-generated identification · may be incorrect

A polished, translucent tan-brown sphere with gray-white chalcedony, honey-colored zones, and dark/golden inclusions; vitreous to waxy luster. Mohs hardness 6.5–7, cryptocrystalline quartz structure, no visible cleavage, specific gravity about 2.6.

Identified September 12, 2026More gemstone →

Explore Polished chalcedony (likely sagenite or included agate) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

At a glance

Common name: Polished chalcedony (likely sagenite or included agate)
Scientific name: Microcrystalline quartz, SiO₂, with iron-oxide and possibly rutile/goethite inclusions
Category: gemstone
Identified: September 12, 2026
Method: Standard

AI Estimated Value

Approximately $10–$50 for a common polished sphere; $50–$150+ for larger, unusually attractive, or strongly included specimens.

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 chalcedony in bands and trapping iron oxides or other minerals; inclusions and color develop during later mineralization. Typically Cenozoic to older volcanic-host-rock age.

Uses & applications

Used as a decorative sphere, lapidary ornament, paperweight, and collectible gemstone; similar included agates are also used in cabochons and jewelry.

Geological facts

The internal patterns are natural mineral inclusions rather than visible quartz crystals. Strong translucency and irregular flow-like banding are characteristic of chalcedony-based agate.

Field identification & locations

Identify by its cool, dense feel, glassy polish, translucency, and resistance to scratching by steel; glass or resin may show bubbles, but testing should be done inconspicuously. Common sources include Brazil, Uruguay, Mexico, Madagascar, and the United States.