Jasper conglomerate, from Sault Ste. Marie, middle Precambrian, Huronian supergroup rocks, 2,200 – 2,450 million years ago. The jasper conglomerate was formed in river deltas draining a landmass to the north. This sediment formed a thick wedge of material, similar to that forming today in the Mississippi Delta. Most of the rock is composed of quartz pebbles. The striking red pebbles in the rock are a type of quartz called jasper. Jasper conglomerate is used as a decorative stone. The material takes a good polish.