Fluoborite; New Method Mine, Bristol Mountains, California
We haven't been able to dig up a lot of information on this material. We picked up this piece from a rock shop near the mine, so we assume the id is correct. Really interesting, fibrous material. Shown here in Shortwave, Longwave, and Natural. We've added a very, very long exposure of the piece in MW just because it looks cool. About 4 inches across.