This datolite nodule from the Delaware Mine, Delaware, Keweenaw County, Michigan, USA. This was an underground copper mine that was active until the late 19th century. It is famous for the variety of datolite nodules that were found there. They can be found in a variety of colors including white like this piece. The nodule was been sawed in half and polished to a gem luster giving it a porcelain-like appearance. Photo 4 shows the natural surface on the rear side of the piece. It measures 3 x 1 3/4 x 1 inches or 76 x 45 x 25 mm.