omar

noun1

1. •
   A glacial erratic piece of (typically smooth) dark siliceous greywacke that exhibits a hemispherical pit or hole (as a result of selective dissolution of carbonate concretions within the greywacke), originating in the Omarolluk Formation and carried by glaciers throughout Canada and the United States.

   • [...] Omarolluk Formation serves to distinguish omars from wacke clasts derived [...] an omar dispersal "limit" in Northern Ontario is difficult to reconcile [...] — 2000