Gypsum

specimen number:
1655513

location:
Laguna del Rey, Ocampo, Coahuila, Mexico

description:
A glassy gemmy colorless fishtail twinned gypsum crystal grouping. In good condition with minimal damage present as shown. This is classic Mexican material.

Laguna del Rey, located in the municipality of Ocampo in Coahuila, Mexico, is a vast playa lake and evaporate basin renowned for its massive industrial production of sodium sulfate and magnesium minerals. Geologically, the deposit formed within a closed bolson or terminal basin where mineral-rich waters evaporated over thousands of years, leaving behind thick layers of gypsiferous muds and brines. This specific environment is famous among mineral collectors for producing spectacular "fishtail" contact twins of gypsum (selenite), which form when two crystals grow together in a mirrored orientation that resembles a fish tail or a swallowtail. These crystals are often translucent to transparent, frequently containing inclusions of the surrounding gray or brown clay. Historically, large-scale industrial mining began at the site in the early 1960s with the establishment of the Quimica del Rey plant by Industrias Penoles. While the primary focus of the operation from 1964 to the present has been the extraction of chemicals for the detergent and paper industries, the world-class gypsum twins are frequently recovered by miners and local prospectors during the excavation of the saline sediments.

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