A large, somewhat silky and translucent to transparent gypsum (variety selenite) cleavage sample. Most notable for its historical provenance: ex William Jefferis (1820-1906) and ex Carnegie Museum. Jefferis was one of the earliest significant American mineral collectors, amassing a collection of 14,000 specimens, which was purchased around 1900 by Andrew Carnegie then donated to the Carnegie Museum in Pittsburgh. The corresponding handwritten Jefferis label (catalog number 7606 and an acquisition date of November 1, 1873!) and Carnegie Museum label accompany this significant specimen.