sedimentary

Puddingstone / polymictic conglomerate

Polymictic conglomerate, chiefly quartz, feldspar, and lithic clasts in a silica-rich or carbonate cement

AI-generated identification · may be incorrect

Hardness varies roughly 6–7 for quartz-rich portions; pale gray-white matrix with rounded brown, black, and translucent clasts, vitreous to dull luster, and no consistent cleavage. The rounded pebbles and visibly cemented texture are diagnostic.

Identified September 10, 2026More sedimentary →

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At a glance

Common name: Puddingstone / polymictic conglomerate
Scientific name: Polymictic conglomerate, chiefly quartz, feldspar, and lithic clasts in a silica-rich or carbonate cement
Category: sedimentary
Identified: September 10, 2026
Method: Standard

AI Estimated Value

About $10–$50 for a common hand specimen; $50–$150 or more if unusually attractive, well-crystallized, or provenance-documented.

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

Formed when water-worn pebbles and sand accumulated in a river, beach, or alluvial setting and were lithified by mineral cement; its exact age cannot be determined from the image. Some examples are glacial conglomerates or ornamental “puddingstones.”

Uses & applications

Used as decorative and landscaping stone, architectural aggregate, and collectible material; attractive polished pieces may be used for bookends or cabochons.

Geological facts

The specimen appears unusually vuggy and mineral-rich, with possible quartz or calcite druse and dark volcanic or iron-bearing clasts. “Puddingstone” is a trade and descriptive term rather than one unique geological composition.

Field identification & locations

Identify it by rounded, compositionally varied clasts firmly embedded in a finer matrix; acid fizzing would indicate calcite cement, while quartz-rich areas scratch glass. Common in ancient river gravels, glacial deposits, and conglomerate beds worldwide.