This specimen exhibits 2 habits of prehnite, all formed as casts after anhydrite. It has both the form of "stalactite"-like prehnite after anhydrite that look just like fingers, formed by thicker prehnite casting and overtopping anhydrites that then dissolved away; and it has others crystals that have a sharp, more anhydrite-looking appearance with nice angles. All are very lustrous, translucent with fine light apple-green color. Hollow casts of what were once anhydrite can easily be discerned looking up from the bottom. A large, dramatic, and very interesting specimen showing exactly how these kinds of minerals form as replacements of previous species. It is also big and showy, as well as educational in that regard... the best of both worlds for a pseudomorph. As a classic US piece, this cabinet specimen would have looked at home in any museum as a typical example of what was found here a century ago, but such large pieces are rare (then and now), and few would be in such good condition.