Pentahydroborite is a rare hydrated calcium borate mineral found only at a handful of deposits in the world. This large piece for the species originates from the skarn deposits at the Fuka mine in Japan, the same locality as the beautiful blue henmilite crystals. Pale gray-blue and tan, coarse, granular massive pentahydroborite forms the core of the piece and is topped by several, colorless to white, translucent to gemmy triclinic crystals to nearly one centimeter. As an added bonus, it fluoresces purple-violet under long-wave UV! A great piece for the species! This is one of the larger specimens from the remarkable find here of the late 1990s. I have not seen them for sale since.