In the early part of 1890 I noticed in some of the workings of the Torreon Mines, and chiefly on a decomposed ehalcopyrite or in close connection therewith, a greenish-blue to sky-blue lamellar coating about inch in thickness, with sometimes isolated plumose groups of scaly crystals having a pearly lustre. Both appearance and mode of occurrence of the mineral led me to think it a basic sulphate of Copper, probably cyanotriehite, or possibly a new species. Soon afterwards however, it was noticed that when the ore, as sorted for smelting, contained any quantity of the pale blue incrustation the cyanide assay failed to give accurate results in the estimation of copper, and on testing such ore qualitatively for zinc quite an appreciable quantity was found. Want of leisure prevented a more extended examination, but a good many specimens were selected and carefully preserved.