Terlingua calcite is one of the most spectacular and beautiful fluorescent minerals due to its bright, multi-colored, multi-wave, fluorescent response, and bright, persistent phosphorescence. Terlingua calcite shows bright blue fluorescence under short wave UV, with bright and long-lasting phosphorescence. Under long wave UV, the fluorescent response is bright pink. True Terlingua calcite comes from only one source- the mercury mines of Terlingua, Brewster County, Texas, with the most notable location being the Little 38 Mine, located 4 miles west of Terlingua. These mines have been closed for years, and many have been reclaimed, making the collection of new material very difficult, if not impossible. Calcite showing a similar fluorescent response, but collected from other locations, is referred to as “Terlingua-type” calcite. The size of this specimen of Terlingua calcite is 13.3 x 6.4 x 5.4 cm, and it weighs 333 grams.