Square prismatic "wernerite" crystals to 4cm. Wernerite is a member of the Scapolite series. This is an antique specimen with a "John H. Caswell" label. Casewell was a famous petrologist/mineralogist during the late 1800's. His works are presented in several early USGS publications for petrological works, such as thin sections to describe rock types of a particular area. A good example is the historic publication of Newton & Jenny's report on the Black Hills. A short biblio is presented on the Mineralogical Record Label Archive, an incredible reference guide to historic and contemporary collectors with label examples.
Please see the provenance tab for his label, which accompanies this specimen.