1.7" Polished Kona Dolomite Hearts - Michigan

About Kona Dolomite

Kona Dolomite is a stromatolitic rock from the Kona Formation of the Chocolay Group in Michigan’s Upper Peninsula, dating to the Paleoproterozoic Era about 2.2–2.3 billion years ago. The rock formed in a shallow marine environment where microbial communities built layered structures known as stromatolites. In the Kona Dolomite these fossil structures are commonly attributed to the stromatolite species Collenia undosa, which produced the characteristic domed and wavy laminations preserved in the rock. When cut and polished, Kona Dolomite reveals striking cream, gray, and brown banding that reflects the original growth layers of these ancient microbial colonies.

Stromatolites are layered sedimentary structures created by colonies of microorganisms—primarily photosynthetic cyanobacteria—that trap and bind sediment while growing in sunlit, shallow water. As the microbial mats grow upward toward light, they form thin layers that accumulate over long periods of time, eventually building domes, columns, or laminated sheets in the rock record. Stromatolites represent some of the oldest evidence of life on Earth, with examples known from rocks over 3.4 billion years old. The stromatolites preserved in the Kona Formation, including those assigned to Collenia undosa, record ancient microbial ecosystems that thrived in early seas long before complex plants and animals evolved.