Most of the developed molybdenum deposits of _Mexico_ are in the State of Sonora. In the Sahuaripa district of eastern Sonora, the mineral occurs with scheelite in rich pockets containing very large pieces of pure mineral. Some molybdenum ore has been shipped from the Montezuma copper district to the Empire Smelting & Refining Co., of Deming, New Mexico. Molybdenum is reported in several other Sonora localities. Near Coyame and Marquez, northeastern Chihuahua, the mines of the Compañia Minera Aurora y Anexas produce molybdenum ore. Wulfenite is found abundantly with the lead ore of the Cuchillo Parado mine in the same district. The Jibosa copper mine of the American Smelters Securities Co., near Jimenez, Chihuahua, seems to carry considerable oxide of molybdenum, molybdite. It is not commercial at present. Molybdenite deposits are also reported in the states of Sinaloa, Oaxaca, Hidalgo, and Jalisco. RESERVES As the production of molybdenum ores in the past in all countries has been relatively small, probably none of the deposits have been worked out and an increased output can be obtained. This applies particularly to the United States. All of the work that has been done so far has been on an experimental basis, and possibly the only mine whose tonnage will be decreased by past production is the Mammoth mine, near Mammoth, Arizona, and there is no certainty that this mine can not continue to produce as much for some time in the future as it did during its period of operation. Just what production can be obtained in the United States is somewhat uncertain, but it is probable that the deposits at Climax, Colorado, will yield at least one thousand tons of ore a day for several years and possibly for a good many years. The deposits of the Primos Chemical Co. near Empire, Colorado, are also extensive and should give a large output for some time to come. The rest of the deposits mentioned are small compared with these two, but the total production of all of them might be large, were a steady market assured and custom mills erected. TREATMENT OF ORES In concentrating wulfenite ores some form of table concentration, with the addition of slimers, is generally used. The metallurgical treatment of the concentrates varies and is still very much in the experimental stage. There is opportunity for the development of a process that will give the patentee a considerable advantage over competitors. The Bureau of Mines has been working on this problem and has recently devised a method that seems to be as efficient as any other and possibly has some additional advantages.