Duquesne-Washington Camp, Patagonia Mining District, Patagonia Mountains, Santa Cruz County, Arizona, USAi

Regional Level Types
Duquesne-Washington Camp	Mining District
Patagonia Mining District	Mining District
Patagonia Mountains	Mountain Range
Santa Cruz County	County
Arizona	State
USA	Country

A Zn-Pb-Cu-Ag-Au (W) mining area located in sec. 34, T23S, R16E, and secs. 2 & 3, T24S, R16E (protracted), in the western part of the district, about 3 miles south of Mowry and the same distance north of the Mexican boundary. This group is situated on the lower eastern slope of the Patagonia Mountains at an elevation of about 5,500 feet. The two camps (Washington & Duquesne) are ¾ mile apart. A large group of mines comprising 80 claims, of which 42 are patented, and covers 1,600 acres of mining ground. It extends beyond Washington on the north and to points about a mile west and southwest of Duquesne on the south. Owned chiefly by the Duquesne Mining & Reduction Co. of Pittsburgh, PA, with local headquarters at Duquesne, and the reduction plant at Washington.

Duquesne was a thriving mining camp town at one point, it is now a ghost town. The mines were in and around the town that depended on the mining for its existence. The town had a schoolhouse, bar/brothel and residences. The town has recently sold and the new owners are busy restoring the buildings, and would like to make it clear that the land including all tailing dumps are strictly off-limits and trespassers are not welcome.

The surface in general slopes gently eastward. The topography is hilly and in the western part mountainous but in few places rough.

The country rock, locally called 'quartzite and limestone,' consists mainly of limestone with a small amount of quartzite and other sediments occupying a north-south belt 2½ miles long and, between the two camps, about 1¼ miles wide. This belt is almost surrounded by igneous rocks, being bounded on the north-west, west, and south by quartz monzonite, locally called 'granite,' and on the east principally by granite porphyry. Both of these latter rocks also occur as detached masses and dikes in the belt and are seemingly intrusive into the sedimentary formations. Both the quartz monzonite and the sedimentary rocks are cut by dikes of aplitic granite, and also by diorite (?) dikes.

The rocks in general have been much disturbed and apparently overturned but seem to be conformable. They dip steeply to the west, mostly at angles of 60º or more, but locally the dip varies greatly in direction and amount. The older members - the quartzite, some of which is micaceous, and the more altered limestone - occupy the upper position in the section next to the quartz monzonite on the west. The limestone is medium to heavy bedded or massive. In the western part of the camp it lies in crude north-south bands or zones of relatively pure rock, alternating with rock that is impure, metamorphiosed, silicated, or cherty. In places it contains some interbedded quartzite. The limestone is contact metamorphosed to white and bluish or greenish crystalline marble, much of which is coarse-grained. In places the rock is otherwise altered and silicated.

At intervals, mainly along the contact with the igneous rocks, particularly the quartz monzonite, and to a less extent as inliers in the sedimentary area, roughly paralleling the bedding of the limestone, occur extensive and well-developed garnet zones from 10 to 100 feet or more wide, containing the usual assemblage of other contact-metamorphic minerals. NOTE: The ground in the area literally sparkles everywhere along the roads from the garnet crystal faces reflecting the sunlight.

A body of the limestone which has escaped the metamorphic effects of the intrusive granite porphyry within a few hundred feet of the contact, at a point about ¼ mile north of Duquesne, is dark bluish, compact, and indistinctly stratified and contains seams or veinlets of calcite approximately parallel with the bedding. This rock is lithologically identical with the dark Pennsylvanian limestone of Sycamore Ridge, in the crest of the Santa Rita Mountains east of Helvetia, and at the Total Wreck Mine, in the Empire Mountains. It is also seemingly similar to the Martin limestone (Devonian), at Bisbee.

The most extensive exposure of the quartzite is along the western edge of the sedimentary belt, where it intervenes between the limestone and the quartz monzonite and probably forms the basal member of the sedimentary series. These sedimentary rocks are at least several hundred feet in thickness.

The quartz monzonite is a greenish-gray, black-speckled granitoid rock with a reddish tinge and weathers reddish-brown. It is medium- to coarse-grained and locally porphyritic. It is fairly fresh and is composed principally of oligoclase, oligoclase-andesine, quartz, orthoclase, biotite, hornblende, augite, and magnetite and contains considerable pyrite and some titanite. The plagioclase, which is the main constituent of the rock is especially fresh. It occurs mostly in stout or elongated prisms, some 0.3 inches long, and it is well-striated, the striations being conspicuous to the unaided eye on fresh surfaces. The general coarseness of the quartz monzonite indicates that it was probably intruded into the sedimentary rocks at considerable depth.

Aplitic granite occurs as dikes, some of which are associated with the ore deposits. It is a relatively fresh, dull-gray, fine- or medium-grained monzonitic rock, composed mainly of orthoclase and quartz with a moderate amount of oligoclase, a little biotite and hornblende, accessory apatite and zircon, and secondary hematite.

Mineralization is tabular to lensing, massive to spotty, pyrometasomatic and replacement deposits of varying amounts of sphalerite, galena, chalcopyrite and pyrite at the margins of skarn zones or along fault zones in faulted and folded Permian Naco Group limestones with intrusions of Laramide granodiorite. Oxidized to various depths. Skarn is largely garnet with other calcium silicates. Minor tungsten is found in the skarn zones.

The metamorphic minerals occuring in the contact zones of the limestone consist mainly of garnet, quartz, and several varieties each of the amphibole and pyroxene groups, sulphides, magnetite, tourmaline and arsenic.

The quartz occurs mostly in irregular masses locally developed in association with the andradite along the contact zone and in the impure cherty zones or metamorphic bands in the sedimentary rocks. Here and there it replaces chert and the earlier metamorphic minerals, such as calcite and actinolite, whose crystalline forms are preserved in masses of relatively pure pseudomorphic silica. On the Belmont and Lead King ground, in the southwestern part of the camp, occurs a body of mainly massive, vitreous quartz, 100 feet (30 meters) wide, containing bunches or clusters of coarsely crystalline material with some crystals 2 feet (60 cm) long and 5 inches (12.5 cm).

The amphibole minerals are principally hornblende, tremolite, actinolite, and gedrite, Of these, tremolite is the most abundant and is intimately associated with many of the ore deposits as gangue.

The deposits, broadly speaking, are principally replacement deposits in the limestone. They occur mainly in or near the metamorphic zones along the limestone and quartz monzonite contact and are also associated with the north-south metamorphic zones in the limestone and other sediments away from the contact. The latter zones are probably connected with the quartz monzonite in depth if not at the surface.

The deposits occur mostly in irregular bodies in or near the garnet formation of the zones and the adjoining limestone.

Workings include extensive shaft, tunnel, and open cut operations but generally shallow (to not over 300 to 500 feet in depth). High-grade Pb-Ag oxidized ore was prospected and mined out by Spaniards, Mexicans, and early Americans prior to 1880. Sporadic large scale mining in the 1900's through 1966. Production would be some 350,000 tons of ore averaging about 6% Zn, 3% Pb, 3% Cu, 6 oz. Ag/T and minor gold.

NOTE: Some references written by Norman Lehman began calling this area a District and then a Mining District, in contradiction to previous references. For the discussion about the name change see: https://www.mindat.org/mesg-644113.html