Analysis of the tetrahedrite from Huallanca, Peru

IN this Journal for April, 1878, there is given a short extract from an article in the London Mining Journal by Mr. Henr.Y Sewell, F.RG.S., describing the mineral caves of Huallanca, Peru. Mr. Sewell states that these silver·producing caves are situated upon the eastern flank of the Peruvian Andes at an altitude of 14,700 feet above the sea, and 4000 feet above the town of Huallanca. The mass of the argentiferous ores consists of the mineral tetrahedrite; these ores contain about 800 ounces of silver to the ton. The mineral is in :fJart obtained from huge cavities, some of them twenty-five or thirty feet long, and as much deep. Mr. Sewell describes the crystals as occurring in such abundance on the walls of these caves, that "millions" of them are destroyed b.y the picks of the miners. Some specimens from this locality were presented to the Yale College Museum by Mr. Sewell; the crystals are large and brilliant and in one case have a length of about two inches. They have the usual characteristic tetrahedral form. I have analyzed a portion of one of the crystals, and have obtained the following results: Specific gravity =4'7.