Terlingua-Type Calcite, San Vicente Mine, Coahuila, Mexico
Contributed by: Chris Clemens
minID: 33W-29K
Date: Apr 24th, 2026
Locality: San Vicente Mine, Boquillas Del Carmen, Ocampo Municipality, Coahuila, Mexico (See on Mindat)
Size: 5.1 x 5 x 6.6 cm
Description:
Terlingua-type calcite shows a similar response to UV light compared to true Terlingua calcite, from the Terlingua, Texas, area. True Terlingua calcite shows bright blue fluorescence under shortwave UV, with bright and long-lasting phosphorescence. Under longwave UV, the fluorescent response is bright pink. True Terlingua calcite comes from only one source however, the mercury mines of Terlingua, Brewster County, Texas. Calcite showing a similar fluorescent response, but collected from other locations, is referred to as "Terlingua-type" calcite. Due to mine closures and reclamation, true Terlingua calcite has become increasingly difficult to collect and is therefore somewhat scarce. However, Terlingua-type calcite from various locations is still relatively abundant and easy to obtain.
This is a specimen of Terlingua-type calcite, from the San Vicente Mine, Boquillas Del Carmen, Coahuila, Mexico. Much of the Terlingua-type calcite from Coahuila, Mexico, has been treated with hydrochloric acid, creating a smooth, rounded, surface. Although the acid-treatment affects the surface appearance of the calcite, it does not affect the fluorescent properties of the mineral. Though cosmetically altered, these Mexican Terlingua-type calcites provide spectacular fluorescent specimens.
Originally posted by Chris Clemens on Nature's Rainbows in 2016.
Summary of luminescence responses:
Calcite (Mindat) (RRUFF)
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue
- Afterglow after exposure to Shortwave (254nm Lamp/Mercury) UV light: Blue
- Fluorescence under Longwave (365nm LED) UV light: Pink