In a paper in Zts. f. Kryst. IX. 186, Professor Laspeyres states that the yellow enerustation uponFelsSbanya stibnite is not ecrvantite, but a sulphide of zinc, which he determines to be wurtzite, chiefly on the optical ground that a black interference cross was observed between crossed nicols, for the chemical proof based on the solubility in cold concentrated hydrochloric acid can hardly be regarded as very conclusive, considering the fact that he had no true wurtzite with which to make the comparison, but only so-called schalenblende, spiauterite, etc. On this account it seemed desirable to test the solubility of wurtzite in HCl, and accordingly a series of experiments as to the comparative solubility of wurtzite, spiauterite, voltzite and different varieties of blende was made by treating small fragments with cold concentrated HCl, (as was done by Professor Laspeyres) in small tubes, in the mouth of which strips of lead acetate paper were inserted.