Allophane is an unusual blue mineral because, unlike most other blue minerals, it contains no copper. It is amorphous, like opal, and can have a similar glassy to resinous luster. It also has some clarity and a conchoidal fracture. This specimen is from a district famous for its smithsonite, which are actually much easier to find, as specimens, than allophane. The allophane vein extends almost all the way through this rock, which measures 7 x 3.5 x 4.5.