Puddingstone (Conglomerate)

Physical Properties

Hardness: 6.5-7 (variable based on matrix and clasts); Color: tan or yellowish matrix with brown, reddish-purple, and black rounded pebbles; Luster: dull to vitreous; Crystal structure: Non-crystalline matrix with rounded clasts; Specific gravity: 2.6-2.8

Formation & Geological History

Formed through the lithification of rounded river or beach gravel transport in high-energy water environments. These specific types, often found in the UK or Great Lakes region, represent ancient glacial or fluvial deposits, frequently from the Proterozoic or Palaeogene eras.

Uses & Applications

Used primarily as decorative stone, in lapidary work for cabochons and paperweights, and historically as a sturdy building material in local architecture.

Geological Facts

The name comes from the resemblance to a traditional boiled fruit pudding. The 'Hertfordshire Puddingstone' was once believed to have magical properties that could ward off evil spirits.

Field Identification & Locations

Identify in the field by the distinct rounded pebbles (clasts) cemented together in a finer-grained matrix. Found in glacial till, riverbeds, and coastal regions like the UK's Home Counties or the Great Lakes of North America.

Identified on: 5/3/2026

Mode: Standard