‡Ref.: Jahns, R.H. (1952), Pegmatite deposits of the White Picacho district, Maricopa and Yavapai Counties, Arizona, Arizona Bureau of Mines Bull. 162: 39, 41 (Plate X), 45, 47 (Plate XIII), 48 (Plate XIV), 50, 65, 98-103.
Jahns, R.H. (1953), The genesis of pegmatites, American Mineralogist: 38: 563-598.
Meeves, H., et al (1966), Reconnaissance of beryllium-bearing pegmatite deposits in six western states, U.S. Bureau of Mines Information Circular 8298: 22 (Table A-1).
USGS & Arizona Bureau of Mines, and U.S. Bureau of Reclamation (1969), Mineral and Water Resources of Arizona, Arizona Bureau of Mines Bull. 180 (USGS Bull.871): 98.
London, D. & D.M. Burt (1978), Lithium pegmatites of the White Picacho district, Maricopa and Yavapai Counties, Arizona, in D.M. Burt and T.L. Péwé (editors), Guidebook to the geology of central Arizona, Arizona Bureau of Geology and Mineral Technology Special Paper 2: 61-72.
London, D. & D.M. Burt (1982b), Lithium aluminosilicate occurrences in pegmatites and the aluminosilicate phase diagram, American Mineralogist: 67: 483-509.
Niemuth, N.J. (1987), Arizona Mineral Development 1984-1986, Arizona Department of Mines & Mineral Resources Directory 29, 46pp.
Peirce, H. Wesley (1990), Arizona Geological Survey Industrial Minerals card file.
Sawyer, M.B., Gurmendi, A.C., Daley, M.R., and Howell, S.B. (1992) Principal Deposits of Strategic and Critical Minerals in Arizona, U.S. Bureau of Mines Special Publication, 334 pp.
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 108, 139, 182, 217, 221, 260, 279, 298, 303, 379, 402, 403.
USGS Red Picacho Quadrangle map.
Arizona Department of Mineral Resources El Oro group file.
Arizona Department of Mineral Resources Midnight Owl file.
MRDS database Dep. ID #10009098, MRDS ID #D001769; and Dep. ID #10027532, MRDS ID #M003258; and, Dep. ID #10258983, MAS ID #0040251405.
An open cut Be-Li-Ta-Nb-feldspar-mica-phosphates mine located in the N.½ of NW¼, sec. 31, T.8N., R.2W., along the steep northern slope of Independence Gulch. The mine is now closed; however, it is under active claim for specimen reclamation. Owned by Earl F. Anderson and Sidney B. Anderson of Mesa, AZ; subsequently held under claim by David Shannon, Mesa, for specimen retrieval.
Mineralization is the Midnight Owl, coarsely crystallized, lithium-bearing pegmatites. Several pegmatite dikes are exposed in the mine area, where they form a belt that trends nearly due east. Though broadly tabular, they are very irregular in detail, and bulges, thick, stubby projections, and long, thin branches are common.
The principal dike trends east, but its component segments and major branches are elongate in northeasterly, easterly, and southeasterly directions. It erminates westward in a very large bulge that measures 80 by 140 feet in its nearly rectangular outcrop plan, and a slightly smaller bulge marks the junction of major branches in the eastern part of the mine area. In the central part of the area is a third bulge, 90 feet long and about 40 feet in outcrop breadth, and from it major branches extend southward and northwestward. Between bulges the main dike is 15 to 25 feet in outcrop breadth. Most observed contacts between pegmatite and country rock are steeply inclined, but gentle to moderate dips appear along the margins of the major bulges.
The pegmatites were introduced along fractures, bedding and foliation planes, and along country rock contacts. Emplacement was probably by mechanical injection of liquids, accompanied by local replacement of susceptible types of country rock.
The country rock in the mine area is mainly a dark gray quartz-hornblende-mica gneiss, in which a well-defined foliation trends northeast and dips steeply northwest through most of the mine area.Numerous thick layers of silvery gray quartz-muscovite schist are exposed on the hillside immediately West of the main pegmatite body. The schist contains scattered metacrysts of garnet, chloritoid, and altered staurolite. Schorl is locally abundant in both of these rock types near the pegmatite contacts. The schist and gneiss occur as inclusions and septa in most of the pegmatite dikes, and are particularly abundant near the margins of some bulges. A large septum of schist is exposed in the northwest part of the Upper cut, and several wallrock inclusions have been encountered in the Lower cut. Two tabular masses, 3 feet in average thickness, of greenish-gray, punky-appearing rock may be post-pegmatite dikes of intermediate to basic composition.
Significant additional data regarding the pegmatite, by zones, is provided by Jahns (1952).
Workings include an irregular upper cut and a lower cut. Nearly all of the minking has been done in the thick eastern and western bulges of the main pegmatite body. The upper cut is in the northeast part of the West bulge and is 40 by 50 feet and 25 feet maximum depth. The lower cut, about 150 feet to the East, is a slightly smaller opening in the central part of the East bulge.
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Map Reference: 33°59'57"N , 112°30'48"W
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