sedimentary
Omarolluk
Omarolluk (Siliceous greywacke with hemispherical voids)
AI-generated identification · may be incorrectHard, rounded greywacke cobble. Brownish exterior due to oxidation, often grey inside. Characterized by distinct hemispherical voids, sometimes with a concretion still inside.
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Physical properties
Hard, rounded greywacke cobble. Brownish exterior due to oxidation, often grey inside. Characterized by distinct hemispherical voids, sometimes with a concretion still inside.
Formation & geological history
Formed in the Proterozoic eon in the Belcher Islands, Hudson Bay, Canada. Transported widely across North America by glaciers during the Pleistocene ice ages.
Uses & applications
Valued by collectors and as a geological curiosity due to its distinct appearance and glacial transport history.
Geological facts
Omarolluks are important glacial erratics. Their distinct composition and voids allow geologists to trace the movement of the Laurentide Ice Sheet from Hudson Bay across Canada and into the northern United States.
Field identification & locations
Identified by the dark, dense rock (greywacke) and the perfectly round pits or voids on the surface. Commonly found in glacial deposits, beaches, and riverbeds in areas affected by glaciation from Hudson Bay.
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