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Montosa Mine | |
Alternate NamesAmado, Double O Mining District and MinesTyndall District Historical: Patent Survey Plats (1912) indicate 6 shafts a total 225 feet deep and one tunnel, 50 feet long. Several shafts, adits, and drifts sunk as deep as 250 feet and with 2,000 feet of underground workings (3,5,25).1
USBM: Several prospect pits and cuts that may be remnants of shafts and adits; no underground is accessible. Shaft shown on USGS Mount Hopkins 7.5 min, typographical map and labeled Montosa Mine is partially open but inaccessible. The shaft is not situated on the plot of claims and does not align with workings shown on the historical mapping1. Historical: The Montosa mine is located in the southwesterly part of Montosa Basin and adjoining hills, at an elevation of about 4,900 feet and is easy of access. It is owned by Freeman & Smith, of Tucson. The property comprises a group of 14 claims known as the Montosa group. It was worked principally about 1901 and soon thereafter by Capt. John D. Burgess, of Tucson, for the Calabasas Copper Co. (Ltd.), with headquarters in New York City. The company did about 2,000 feet of underground work, mostly on the Isabella ground. It sunk to a depth of 250 feet and installed a 36-inch 30-ton water-jacket testing smelter. The smelter, however, was operated only 4½ days, but during that time $9,600 worth of bullion was extracted and a two days' run yielded considerable ore, carrying 47% of copper. The ore in general averaged about 8% copper, and the bullion, which was shipped to Ledoux & Co., of New York, carried about 360 ounces of silver and 3.1 ounces of gold. Some of it contained 16 to 20 % of lead and 30 to 45 % of iron (FeO). The ore is said to have contained principally malachite, chalcopyrite, bornite, lead carbonate, galena, magnetite, specular hematite, and in places silicified green epidote. The iron oxides occurred principally in large masses intimately mixed with the malachite. The company gave up the mine to the owner when its bond expired, in February 1902, and since then no work to speak of has been done on it until recently. The deposit is a replacement body in the Paleozoic limestone, which dips to the southwest. It is in the lower part of the limestone near its contact with the underlying shale. It trends about N. 70° W. and lies in a mineralized zone which extends at least one-eighth of a mile to the southeast and beyond which the limestone soon gives way to the overlying andesite that caps the mountains The intrusion of the andesite may be connected with the origin of the ore deposits, as is suggested by the fact that the andesite contains considerable magnetite, the deposits resembling in some respects those on Jackson Canyon, in the Old Baldy district. A 30 by 40 foot open cut, the principal surface exposure, is about all in low-grade ore or bedded mineralized material. The entire mass is very ferruginous, containing magnetite and specular hematite, and the latter is the principle gangue mineral. The copper is represented by malachite, lead-copper oxide, and a little chrysocolla. Sulphides seem to be absent. The best part of the exposure is a 6 foot ferruginous bed that follows a slickensided footwall, dips 75° S., and seems to be the chief source of the ore produced. It is composed of principally magnetite and specular iron and contains a little malachite, red copper oxide, and chrysocolla. About 40 tons of the ore is pilled up on the ground, some of which is sorted for shipping, but it seems to contain little of value other than the iron. In the dump at the smelter the ore, which seemingly had been sorted, similarly consists mainly of malachite and azurite with a little chrysocolla and red copper oxide in a magnetite-specularite gangue. The deposit seems to contain a large amount of low-grade ore and can probably be profitably handled only if it is worked for iron as well as copper.2 Location31.66903N, -110.93398W4 NW¼, sec. 29 Mineral ProductsUSBM: Ag, <0.8 - 49.6 ppm; Au, <5 - 29ppb; Cu, 13 - 9,036 ppm; Mn 1,395 -> 10,000 ppm; Pb, 72 -> 10,000 ppm; Zn 134 -> 20,000 ppm. Also 5 samples, 112 - 462 ppm Bi; 2 samples, 360 & >20,000 ppm Cd; 5 samples, 130 - 540 ppm Cr; 3 samples 202 - 254 ppm Mo; 4 samples, 117 - 547 Sb; and 6 samples, 340 - 1,190 ppm W.1 GeologyIrregular replacement body in large limestone block engulfed in dacitic volcanic breccia, and sporadically mineralized quartz-fissure vein cutting the dacitic breccia. Galena, chalcopyrite, pyrite, and sphalerite are present (20)1. Type of Operation and ProductionHistorical: Intermittent production, 1912 - 1913; 32 cars of ore averaging 32% Pb, 9.0 oz/t Ag, 3.5% Cu. References
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