The Crystal Cave is a limestone cave located in Put-in-Bay, Ohio, located on South Bass Island in Lake Erie. In 1887 a Mr. Gustav Heineman emigrated from Baden-Baden, Germany to Put-in-Bay, Ohio, where he established a winery. In 1897 he dug a well beneath his winery and discovered a large vug at a depth of 30 feet (10 m). On exploring the cave he found the cave walls covered with extremely large and well-developed tabular crystals identified as celestine, a form of strontium sulfate.