San Vito quarry, San Vito, Monte Somma, Vesuvius, Naples, Italy
Small Cabinet, 7.1 x 6.9 x 3.8 cm
Ex. John S. White
Vaterite, according to MINDAT, is a rare CaCO3 modification that is metastable below approx. 400C. I always learned of it as a very rare crystal habit of calcite, but that is technically incorrect according to this entry, because its crystal habit is distinct from normal calcite. In other words, it is a polymorph of aragonite and calcite - same chemistry, different crystal form. I have only in my career seen vaterite from this locality in Italy, and all were older specimens. This is a particularly large and rich piece with sharp crystals to 2 cm. ex Mike Groben collection