sedimentary

Quartz-rich polymict conglomerate (possibly hydrothermal breccia)

Clast-supported polymict conglomerate dominated by quartz; includes chalcedony/quartz and dark lithic clasts

AI-generated identification · may be incorrect

Hardness approximately 6.5–7 (quartz), with Mohs 3–7 for mixed clasts; white to translucent silica matrix, vitreous to waxy luster, rounded pebbles, and no consistent cleavage. The dark brown-black clast may be volcanic rock, iron-stained material, or glassy silica; exact identification requires testing.

Identified September 10, 2026More sedimentary →

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At a glance

Common name: Quartz-rich polymict conglomerate (possibly hydrothermal breccia)
Scientific name: Clast-supported polymict conglomerate dominated by quartz; includes chalcedony/quartz and dark lithic clasts
Category: sedimentary
Identified: September 10, 2026
Method: Standard

AI Estimated Value

$10–$50 for a common hand specimen; $50–$150 for an attractive or documented specimen

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

Likely formed when rounded pebbles and silica-rich material were deposited and cemented, or when silica precipitated through a brecciated rock. Its age cannot be determined from the photograph; similar specimens occur in hydrothermal veins and silicified sedimentary environments.

Uses & applications

Used mainly as a collector specimen or decorative stone; attractive polished pieces may be used in cabochons or ornamental objects, but it has little standard industrial value compared with uniform quartzite or agate.

Geological facts

The specimen shows abundant translucent quartz/chalcedony and strongly mixed clasts, suggesting polymict composition rather than a single mineral. Acid testing, streak, hardness, and thin-section examination would distinguish conglomerate from silicified breccia.

Field identification & locations

Look for rounded clasts cemented by silica, translucent edges, and quartz-like hardness; common sources include hydrothermal districts and ancient alluvial conglomerates. Estimated value is about $10–$50, or $50–$150 if unusually attractive, well-polished, or locality-documented.