Gypsum, var. Selenite (Swallowtail Twin)
This sample of the mineral Gypsum, var. Selenite exhibits distinctive twinning of the rhomboidal crystal, commonly called a swallowtail twin. The specimen is colorless to pale yellow, with gray shale embedded in crevices. It was collected by Thomas Cooper from Baltimore (probably MD) in the early 1800s. The sample has been part of USC's geology collection since 1821, and it is listed as "198a Gypsum, part of twin chrystal, near Baltimore" in the historic Catalogue of the Collection of Minerals in the College of S. C. on page 19.
|Collector||Cooper, Thomas, 1759-1839|
|Place of Origin||Maryland/Baltimore|
Cooper, Thomas, 1759-1839
Catalogue of the Collection of Minerals in the College of S. C.
|Dimensions||H-2.392 W-5.13 L-10.294 cm|