Puddingstone

Physical Properties

Hardness: 6-7 (Mohs scale), Color: Multi-colored with red, white, and brown clasts in a lighter matrix, Luster: Dull to waxy, Structure: Clastic with rounded pebbles, Cleavage: None

Formation & Geological History

Formed in high-energy fluvial environments (rivers) or beach zones where rounded pebbles are deposited and later cemented by minerals like silica or calcium carbonate. This specimen appears to be an 'Ontario Puddingstone' from the Lorrain Formation, dating to the Proterozoic era (approx. 2.3 billion years old).

Uses & Applications

Used primarily as decorative stone, in lapidary work for making cabochons, as ornamental garden stones, and as historically used for millstones.

Geological Facts

Puddingstone was named by early British settlers because the pebbles in the matrix reminded them of boiled suet pudding with raisins or fruit inside. It is the unofficial state rock of Michigan.

Field Identification & Locations

Identify in the field by looking for distinct, rounded 'pebbles' trapped inside a solid, fine-grained matrix. Often found in glacial till or as loose boulders across the Great Lakes region.

Identified on: 4/20/2026

Mode: Standard