sedimentary

Puddingstone (Jasper Conglomerate)

Quartzite Conglomerate (SiO2 matrix with Jasper/Quartz pebbles)

Hardness: 6.5-7 on Mohs scale; Color: Translucent chalcedony/quartz matrix with yellowish-brown, tan, and reddish Jasper inclusions; Luster: Waxy to vitreous when polished or wet; Crystal Structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture).

Hardness: 6
Luster: Waxy to vitreous when polished or wet

Identified July 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed over 2 billion years ago during the Paleoproterozoic Era. Ancient riverbeds deposited rounded pebbles of jasper and quartz, which were later buried, cemented together by silica-rich water, and subjected to low-grade metamorphism/compaction.

Uses & applications

Popular among rockhounds for tumbling, polishing, and lapidary work. Used in making decorative cabochons, jewelry, and ornamental stone displays.

Geological facts

Often called the 'Lorrain Puddingstone' or 'Jasper Conglomerate', famous specimens from the Great Lakes region are widely sought after. The pebble patterns resemble raisins or fruit in a traditional English Christmas pudding.

Field identification & locations

Identified by distinct rounded pebble inclusions of varying colors tightly fused in a smooth, hard silica or quartz-based host matrix. Commonly found along Lake Huron beaches, Michigan's Upper Peninsula, and Ontario, Canada.

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