Note on the pleochroism of Adamite
The mineral adamite (Zns(AsO4)2.Zn(OH)2), discovered by C. Friedel in 1866 on specimens from Chafiarcillo, Chile, has since been found at only two other localities, namely Cape Garonne in France and Laurion in Greece. At the original locality it would appear to be of rare occurrence, since in the literature mention is made of only two specimens.It was therefore of interest to find in the British Museum collection a good specimen of adamite from Chafiarcillo. This was found amongst the hornsilvers, and the associated adamite had been thought to be fluorite, which indeed, at first glance, with its violet colour and good cleavage, it closely resembles in appearance. The crystals are remarkable by reason of their very strong pleochroism, and as this feature of adamite has previously received no mention it has been thought worthy of placing on record.