gemstone

Polished blue chalcedony or dyed agate

Microcrystalline quartz (SiO₂), likely chalcedony/blue agate; exact identification is uncertain from the photo

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, opaque to translucent, blue with white-gray banding or wispy zones, and a vitreous to waxy luster. Quartz has a trigonal crystal structure but occurs here as cryptocrystalline material, without visible cleavage; specific gravity is about 2.6.

Identified August 17, 2026More gemstone →

Explore Polished blue chalcedony or dyed 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 blue chalcedony or dyed agate
Scientific name: Microcrystalline quartz (SiO₂), likely chalcedony/blue agate; exact identification is uncertain from the photo
Category: gemstone
Identified: August 17, 2026
Method: Standard

AI Estimated Value

About $3–$20 for a small polished common piece; $20–$75 if naturally colored, strongly banded, or unusually attractive.

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 deposits chalcedony in cavities and fractures of volcanic rocks, commonly during the Cenozoic or older volcanic episodes; vivid blue pieces may be naturally colored or dyed. The specimen is tumbled and polished.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and inexpensive jewelry; blue agate is also popular in lapidary collections.

Geological facts

Identify it by its glassy polish, quartz-like hardness, waxy texture, and curved or diffuse banding; a steel knife should not scratch genuine quartz. Common sources include Brazil, Uruguay, India, Madagascar, and the United States.

Field identification & locations

Field specimens occur as rounded cavity fillings or nodules in basalt and other volcanic rocks; inspect edges for natural banding and dye concentration. Exact species and treatment require testing or magnification.