On the relation between Rathite, Rathite a, and Wiltshireite

Abstract

At the Society's Anniversary Meeting of November, 1908, I exhibited and gave an account of an unnamed crystal from the dolomite of the Leugenbach quarry in the Binnenthal, Switzerland. In the notice of this meeting, as given in ‘Nature’ of December 10, 1908 (vol. lxix, p. 142), this mineral, which could not be identified with any of the sulpharsenites of lead previously described, is referred to as follows :— ‘One of these [black minerals with metallic lustre] is oblique with β = 81° 11′, (100),(101)= 40° 7′, (010),(111) = 5° 26′; it has a perfect cleavage (100), and, like liveingite, exhibits no oblique striations on the planes in the zone [100,001].’ Owing to lack of material, the chemical composition and specific gravity of this apparently new mineral could not be determined.