There are two operating companies, the Climax Molybdenum Co., a subsidiary of the American Metal Co., of New York and Denver, and the Molybdenum Products Co., of Denver. Both of these companies have erected mills having daily capacities of 200 tons. The mill of the American Metal Co. started continuous operation about March, 1918, and that of the other company was completed shortly afterwards. Both companies claim that they can enlarge the capacity at short notice. The writer was in the mine of the American Metal Co. Evidently a considerable part of the mountain is molybdenite, and without doubt, a very large tonnage can be produced. The Jackling interests recently acquired the adjoining properties owned by the Pingree Mines Co., but in 1918 had not built a mill or carried out any serious development work. Another very large group of deposits of molybdenite lies near Empire, Clear Creek County, Colorado, on the eastern slope of Red Mountain, at an altitude of about 11,000 to 12,000 feet. The deposits are 14 miles from the Empire station of the Colorado & Southern Railroad and are owned by the Primos Chemical Co., of Primos, Pennsylvania. The ore-bearing bodies consist of three veins of low-grade ore. The ore zone, that is, the ground included between the footwall of Vein No. 1 and the hanging wall of Vein No. 3 where cut by the tunnel, is about 200 feet wide. The veins vary greatly in width and are not particularly well defined, thin veinlets and stringers of ore running into the walls. The Primos Chemical Co. has worked these mines off and on for several years. About three years ago it built a mill near the mine, but production has been rather intermittent. This company has probably used all of its concentrates for making ferromolybdenum at its own works in Primos, Pennsylvania. A small mill has been erected at Pitkin, Colorado, in connection with the mine at that place owned by the Pennsylvania Molybdenum Mines Co., of Johnstown, Pennsylvania. A number of other deposits of considerable interest are found in Colorado, especially around Breckenridge, Summit County. Here the pegmatite veins consist largely of muscovite and quartz, with some feldspar, and carry biotite, chalcopyrite and accessory minerals. The difficulty here is to separate the molybdenum from the copper minerals and also from the mica, most of which floats with the molybdenite.