Natrolite, Thomsonite-Ca
Cabinet, 12.1 x 8.1 x 4.0 cm
Hammerunterwiesenthal, Oberwiesenthal, Erzgebirge, Saxony, Germany
This is firstly a very rich cabinet-sized specimen of this rare zeolite species, which seldom crystallizes in zeolite deposits to the same degree as its more common cousins. This specimen is interesting in that it shows layered growth of the thomsonite which served as host for epitaxial crystallization, later, of natrolite. The natrolite crystals are oriented discretely with respect to the underlying thomsonites (this phenomenon is epitaxy), and appear to cover the plate entirely. I had not seen this material before, and am told it is from an old find here.