Tunellite is a rare strontium borate hydrate found as a secondary mineral in borate deposits and this is a large and extremely significant piece for the species! This Tunellite specimen is a lustrous, relatively complex and well-formed, monoclinic crystal exhibiting a wonderful pearlescent luster. The crystal almost has a compound diamond shape when viewing the piece along either side where it's lamellar character resulting from its perfect (100) cleavage can be seen. Faces and edges of the composite monoclinic crystal are really well formed and pronounced, resulting in an exceptional example from this classic and highly productive borate mine in the Death Valley area of California. Although it is a borate, Tunellite is very stable and won't decrepitate. This is certainly one of the better pieces we've seen for the species and few specimens were saved as they were mined. Specimens of this quality are very hard to obtain today. This comes from the Bob Reynolds collection, and we know that he got his borates in trade directly from the collection of the man who collected this and nearly all others, Jim Minette, former manager at the Boron mine. Bob Reynolds was the curator of the San Bernardino County Museum and a longtime California specialist, as well as a trading partner with Jim Minette. Boron was famous for its rare borates like Tunellite and produced the best of the species for this material.