sedimentary

Puddingstone

Conglomerate

Hardness: 6.5-7 (due to silica cement); Color: tan or grayish matrix with rounded colorful pebbles; Luster: dull to vitreous when polished; Crystal structure: clastic texture; Specific gravity: approx 2.6-2.7

Hardness: 6
Color: tan or grayish matrix with rounded colorful pebbles
Luster: dull to vitreous when polished

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in high-energy environments like riverbeds or coastal zones where large pebbles were rounded by water action and then cemented together by fine grained sediment and minerals over millions of years.

Uses & applications

Primarily used as a decorative stone, for garden landscaping, lapidary art (polishing into spheres or bookends), and historically as a construction material for local buildings in areas like Michigan or the UK.

Geological facts

The name comes from its resemblance to a traditional boiled fruit pudding with raisins/nuts. The most famous varieties are the Roxbury Puddingstone in Massachusetts and the St. Joseph Island Puddingstone in Ontario/Michigan.

Field identification & locations

Identify by looking for distinct, rounded 'clasts' or pebbles firmly embedded in a finer-grained matrix. Often found in glacial till or riverbeds. Collectors look for high contrast between the pebbles and the matrix.