Celestine crystals are found in some geodes. The world's largest known
geode, a celestine geode in diameter at its widest point, is located near the village of
Put-in-Bay, Ohio, on
South Bass Island in
Lake Erie. The geode has been converted into a viewing cave,
Crystal Cave, with the crystals which once composed the floor of the geode removed. The geode has celestine crystals as wide as across, estimated to weigh up to each. Celestine geodes are understood to form by replacement of
alabaster nodules consisting of the
calcium sulfates gypsum or anhydrite. Calcium sulfate is sparingly soluble, but strontium sulfate is mostly insoluble. Strontium-bearing solutions that come into contact with calcium sulfate nodules dissolve the calcium away, leaving a cavity. The strontium is immediately precipitated as celestine, with the crystals growing into the newly formed cavity. Celestitemadagascar.jpg|Celestine geode section Crystal Cave Ohio.JPG|Inside the Crystal Cave geode in Ohio ==See also==