sedimentary

Quartz-bearing polymictic conglomerate

Conglomerate with milky quartz clasts; composition may include quartzite and weathered feldspathic/mafic rock fragments

AI-generated identification · may be incorrect

Coarse, rounded-to-subrounded white milky-quartz pebbles in a brown-gray iron-stained matrix; quartz has Mohs hardness 7, vitreous to waxy luster, no cleavage, and conchoidal fracture. The specimen appears naturally weathered, with iron-oxide staining.

Identified September 15, 2026More sedimentary →

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At a glance

Common name: Quartz-bearing polymictic conglomerate
Scientific name: Conglomerate with milky quartz clasts; composition may include quartzite and weathered feldspathic/mafic rock fragments
Category: sedimentary
Identified: September 15, 2026
Method: Standard

AI Estimated Value

Approximately $2-$15 for a common hand specimen; up to $20-$50 if unusually attractive, locality-labeled, or polished.

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 deposited by a high-energy stream, alluvial fan, or beach, then lithified by compaction and cementation; exact geologic age cannot be determined from the image and depends on its locality.

Uses & applications

Common conglomerate is used as crushed aggregate, riprap, and decorative stone; attractive quartz-rich pieces are collected or polished, though this specimen appears mainly of modest specimen value.

Geological facts

Conglomerate is distinguished from breccia by rounded clasts, indicating transport and abrasion before burial. White areas may be milky quartz or quartzite rather than a single large crystal.

Field identification & locations

Look for clearly rounded pebbles cemented in a finer matrix; a hand lens and dilute hydrochloric acid can test for carbonate cement, while quartz remains unreactive. Common in ancient river and shoreline deposits worldwide.