A striking, very lightweight plate of a forest of tannish-white pseudomorphs of tincalconite after sharp, spiky, tabular borax crystals from the U.S Borax Mine of California. This is a highly representative specimen of this rare and very unusual pseudomorph. Excellent material from this famous district. They are so lightweight you really have trouble believing these are natural crystals, but they are. These are superb pseudomorphs. Ex. Mullane Collection.