Terlingua Calcite, a Multi-Wavelength Beauty from the Mercury Mines of Terlingua, Texas

Contributed by: Chris Clemens
minID: C3W-F4T
Date: Apr 22nd, 2026
Locality: Little 38 Mine, Brewster County, Texas, USA (See on Mindat)
Size: 9 x 6 x 15 cm
Weight: 802 g

Description:
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-wavelength, fluorescent response, and bright, persistent phosphorescence. Classic Terlingua calcite is defined by bright blue fluorescence with bright and long-lasting blue phosphorescence under shortwave UV, and bright pink fluorescence with little or no phosphorescence under longwave. Terlingua calcite often shows a lavender-colored fluorescent response under midwave UV with blue phosphorescence. Calcite showing a similar fluorescent response, but collected from other locations, is referred to as "Terlingua-type" calcite.

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.

Originally posted by Chris Clemens on Nature's Rainbows in 2018.