Hull Mine group (Rialto Mine group; Hull group of claims; Rialto claims), Buckeye vein group, Castle Dome Mine group, Kofa Game Range, Castle Dome District, Castle Dome Mts, Yuma Co., Arizona, USA

Ref.: Blake (1880).

Blake, William P. (1881a), Vanadinite in Arizona, American Journal of Science: 22: 235.

Blake, William P. (1881b), On the occurrence of vanadates of lead at the Castle Dome mines in Arizona, American Journal of Science: 22: 410-411.

Wilson, E.D. (1933) Geology and Mineral Deposits of Southern Yuma County, Arizona. Arizona Bureau of Mines Bulletin 134: 99-100.

Phelps, Harlow D. Fluorspar Lead Silver Mines Castle Dome District. War Minerals Report O.

Haury, P.S. (1945) US Bureau of Mines Report on Arizona Lead Co, July, 1945.

Wilson, E.D., et al (1950), Arizona zinc & lead deposits, Part I, Arizona Bureau of Mines Bull. 156.

Wilson, E.D., et al (1951), Arizona zinc and lead deposits, part II, Arizona Bureau of Mines Bull. 158: 111-112.

Van Alstine, R.E. and Moore, R.T. (1969) Fluorspar, in USGS & Arizona Bureau of Mines & U.S. Bureau of Reclamation, Mineral and Water Resources of Arizona, Arizona Bureau of Mines Bull. 180 (USGS Bull.871): 354.

Minerals Availability Systems: Arizona Fluorspar, Arizona Department of Mineral Resources, March 1976.

Keith, Stanton B. (1978), State of Arizona Bureau of Geology and Mineral Technology, Geol. Sur. Br. Bull. 192, Index of Mining Properties in Yuma County, Arizona: 120 (Table 4).

Phillips, K.A. (1987), Arizona Industrial Minerals, 2nd. Edition, Arizona Department of Mines & Minerals Mineral Report 4, 185 pp.

US Bureau of Mines file data cluster 343, Rialto Group.

U.S. Bureau of Mines - Arizona Bureau of Geology and Mining Technology production file data.

Arizona Bureau of Mines file data.

MRDS database Dep. ID file #10103550, MRDS ID #M030326; and, Dep. ID #10186691, MAS ID #0040270030.

A former underground Pb-Ag-F-Ba-V-Mo-Zn-Au-Cu (As-Se-Be-Sb) mine group located in SW¼ sec. 24 & the North-central sec. 25, T.4S., R.19W. (protracted), on the W side of the Castle Dome Mountains; about 3 miles N of Castle Dome Mine, 4 miles SW of Castle Dome Peak, on federal land. Started in 1863. Owned at times, or in part, by Castle Dome Mining & Smelting Co., Gondolfo & Sanquinetti, Mrs. Elizabeth De Luce, Castle Dome Mining Co., Hull Mines, Rialto Co., Joplin Lead Co., Wall, Desert Lead Co., and Taylor. Owned by Mr. G. Hull (1933). The Rialto-Hull group is considered as part of the Castle Dome Mine group.

Mineralization is irregular masses of partly oxidized argentiferous galena in a gangue of fluorite and calcite, up to 12 feet (3.66 meters) wide, and over some 2,000 feet (609.6 meters) in length, in a lensing vein along a fault zone with intersecting faults containing gouge and mineralization. The ore zone has a depth to bottom of 91.44 meters, strikes N30W, and dips 70NE. Some wulfenite and associated vanadinite and vanadiferous mimetite occur in open cavities. Wall rocks are Mesozoic shale, limestone, and sandstone, strongly sericitized with some silicification and chloritization, cut by diorite porphyry dikes. Surface exposures are limited by the gravel cover of the rock pediment. A related rock unit is the Kofa volcanics. Tectonic influences include basin and range block faulting. Ore control was the fault zone containing intersecting faults and gouge. Ore concentration was supergene enrichment.

The vein follows a fault zone in shale. Green, purple, and rose coloured fluorite is associated with calcite, baryte, galena and wulfenite in veins where metasediments have been intruded by rhyolite abd diorite porphyry. Veins split and branch but are traceable for as much as 4000 feet. The fluorspar ore is usually < 5 feet thick.

Workings include stopes worked from a series of shafts down to about 200 feet, and total 518.16 meters in length. Most ore was mined prior to 1900 but fill & dumps were worked to 1960. Total production for the group would be some 20,000 tons or more of ore; about 8333 tons of ore averaging 5% Pb, 2% Cu, 1.96% oz/t Ag, minor Au.