A mostly transparent selenite gypsum cleavage plate, rendered red brown by clay inclusions. 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 759 and an unspecified acquisition date, but judging from the early catalog number, likely 1850's or 1860's!) and Carnegie Museum label accompany this significant specimen.