This is a large, well-formed, prismatic single crystal of Willemite var. Troostite in a matrix of Calcite! It is an old specimen, certainly from the 1800s or early 1900s era, and is accompanied by Gerstmann Franklin Mineral Museum label. The big crystal measures 6.2 cm in length, 3 cm in width and is complete all around, fully terminated and DOUBLY terminated as well - and just exceptional! It exhibits a rich salmon-pink color and contrasts nicely with the adjacent white Calcite matrix. Needless to say this piece is spectacular under short wave UV with the Willemite glowing an incredibly bright neon green in contrast to the vibrant red of the Calcite. This is a high-end Willemite piece with great provenance from both the Gerstmann and Cook collections. Gerstmann had a private museum, and dealership for his duplicates, in Franklin town (more at : https://www.fomsnj.org/Memorial.aspx?kn=102&Last=Gerstmann). MINDAT notes the following: Operator of a private mineral museum and collectors' gathering spot at Franklin, NJ, for many years. The Gerstmann mineral collection was donated to the Franklin Mineral Museum.