Karlsbad Sprudelstein

An unusual sedimentary rock with coated grains (ooids) of aragonite found in the Czech Republic. Thin layers of aragonite form around various internal structures, and needles of aragonite cement keep the grains together like a natural glue. Light micrograph of a petrographic thin section; image produced by stitching together over 100 individual photomicrographs. Sample provided by Axel Munnecke.