Ivanhoe Mine (Commercial Tunnel and Shaft; Ivanhoe 1-8 claims; Commercial 1-6 claims), Squaw Gulch area, Tyndall District, Santa Rita Mts, Santa Cruz Co., Arizona, USA

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A former small underground Ag-Cu-Pb-Au-Mo-Zn-Sb mine located on 22 claims in south central (E½E½SW¼) sec. 34, T21S, R15E, 3 miles NW of Patagonia and 3 miles east of the Montezuma mine, on the east side of an eastern tributary of Squaw Gulch, in the upper part of the ridge which separates this gulch from Smith Gulch (west of Smith Gulch), ¾ mile S of Johnson Spring, at an elevation of about 4,600 feet, on National Forest land. Worked by Mexicans as early as the 1850's. Relocated in 1905. Operated until 1924. Owned at times, or in part, by the Ivanhoe Mining Co., Minneapolis, Minnesota (1906-circa 1915); Johnson; Tobin & Beasley; and, Hopkins.

Mineralization is irregular, crudely-banded, iron and manganese stained, quartz-fissure vein containing spotty ore shoots of chalcopyrite and pyrite and small pockets of galena. Oxidation and supergene enrichment produced copper carbonates, cerussite, wulfenite and silver halides. The ore zone is 12.19 meters wide, with a depth to bottom of 182.88 meters, and a thickness of 182.88 meters, striking E-W, and dipping 80SE.

The country rock is red granite, locally called quartz porphyry from the strong contrast of its greasy-lustered quartz with the red feldspars. Some of the feldspars are altered to the pale-greenish or whitish kaolinized and sericitized stage. The rock is a medium-grained granitic rock composed almost wholly of orthoclase and quartz. Some of the orthoclase is microperthitic. In the vicinity of the mine the granite is considerably leached. The associated rock units are the Squaw Gulch Granite; Lower Member of the Temporal Formation; and, rhyolite tuff and tuff breccia.

On the east the granite is overlain by gray andesite, which ascends the slope to a point about 150 feet above Smith Gulch and the Commercial tunnel, and in the tunnel at this place diorite seemingly intermediate in age between the granite and the andesite is also present.

A portion of the ridge is capped by reddish, partly silicified andesite tuff or 'burnt rock,' which near by and in the mine seems to be intrusive into the granite and is said to contain generally fair amounts of silver. Both the granite and the andesite are sliced by a north-northwest sheeting with steep easterly dip.

The mine seems to be in part on the easterly extension of the Montezuma vein, which here dips 80ºSE and with a vertical range of 600 feet trends across the ridge into the head of Smith Gulch where the Commercial tunnel opens the vein.

The tunnel is mainly in andesite, but upfaulted greenish diorite forms the hanging wall of the drift and fissure on the south. The vein is shown here to be 4½ feet wide and consists mainly of irregularly, coarsely, and crudely banded brownish iron-stained and whitish silicified and kaolinized altered and mineralized rock breccia and quartz. It is more or less porous or honeycombed, and in places, particularly in the face of the drift, it contains small pockets or bodies of galena, some cerussite, and a little wulfenite. Associated with the ore minerals are also some epidote and manganese and iron oxides.

On the westerly slope of the ridge to the south of the Montezuma vein occur two veins or lodes which trend in a northerly direction, about parallel with the ridge and the sheeting structure in the rock, and obliquely to the transverse Montezuma vein. The western vein is known as the sulphide vein and the eastern one as the horn silver vein.

The sulphide vein is about 10 feet wide and has fairly good footwalls, and the mineralized zone containing it is about 28 feet wide. It is a blind vein, without croppings other than a little brecciated gouge. It was first encountered in the shaft about 50 feet below surface. In a raise from the south drift at the bottom of the shaft the vein contains a 4 foot wide oreshoot, which contains mainly of crushed granite intruded by dark andesite, all more or less ferruginated and silicified. It carries chalcopyrite and acanthite at 140 oz. Ag/T and 12% Cu. In the north drift at the bottom of the shaft, a 16 inch (40 cm) oreshoot on the east or hanging wall side of the vein, which is banded, is richer than the corresponding part of the vein in the south drift. It contains considerable chalcocite averaging 21% Cu and 300 oz. Ag/T.

The horn silver vein lies about 100 feet east of the sulphide vein, in altered granite, and is seemingly associated with an andesite dike. It is opened by a 90 foot crosscut tunnel connecting with a 120 foot inclined winze, with about 150 feet of drift on the tunnel level and much more at the bottom of the winze. It is several feet in width and at about 140 feet below the surface changes from a steep westerly dip to a steep easterly dip. It is composed mainly of crudely banded silicified iron and manganese stained crushed rock and quartz. The ore occurs in stringers or streaks from 1 inch to several inches in width and carries good values. It contains mainly chlorargyrite and embolite.

Workings circa 1915 include about 300 feet each of tunnels, drifts and shafts to a depth of about 250 feet, with plans to sink to 400 feet. The Commercial tunnel is 200 feet long and opens the vein at 4,300 feet of altitude at the head of Smith Gulch. The workings totalled 822.96 meters in length and 76.2 meters in depth. Worked by Mexicans as early as the 1850's, and by others through 1924. Produced some 420 tons of ore averaging about 51 oz. Ag/T, 2% Cu and minor Pb. Altered area S of the Ivanhoe asssayed at 50 ppm Ag, 0.9 ppm Au, 150 ppm Mo, 300 ppm Sb, 30 ppm Be, and 200 ppm Bi, especially near the N & E margins of the altered area.

Mineral List

Acanthite Alunite Azurite Cerussite Chalcocite Chalcopyrite

Chlorargyrite var: Bromian Chlorargyrite Epidote Galena Kaolinite Muscovite var: Sericite

Orthoclase Polybasite Proustite Pyrite Silver Stromeyerite

Tenorite Tetrahedrite Wulfenite

21 entries listed. 19 valid minerals.

References