Some calcite specimens collected from the area of Terlingua, Texas show one of the most spectacular and beautiful examples of fluorescence and phosphorescence in the mineral kingdom. Known as Terlingua calcite, these specimens are known for their bright, multi-colored, multi-wavelengh, fluorescent response, and bright, persistent phosphorescence. Classic Terlingua calcite is defined by bright blue fluorescence with bright and long-lasting blue phosphorescence under short wave UV, and bright pink fluorescence with little or no phosphorescence under long wave. Calcite showing a similar fluorescent response, but collected from other locations, is referred to as “Terlingua-type” calcite. The following composite image shows the classic fluorescent and phosphorescent response that Terlingua calcite is known for.
True Terlingua calcite comes from only one source- the mercury mines around the town of Terlingua, in 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. The specimen shown here features a large exposure of brightly fluorescent calcite on a weakly fluorescent limestone matrix, and was collected from the classic source for Terlingua calcite; the Little 38 mine. It measures 15 x 9 x 6 cm, and weighs 802 grams.
The following scrolling images show a closer view of the classic fluorescent and phosphorescent response of Terlingua calcite:
Mouse over the scrolling image for wavelength and other information.
As is the case for this specimen, Terlingua calcite often shows a lavender-colored fluorescent response under mid wave UV with blue phosphorescence.
The left image shows the lavender-colored fluorescence under mid wave UV (302nm) and blue phosphorescence after mid wave UV, right. Click on the above images for a larger view.