Pioneer-Lilyama Mine (Lilyama Mine; Lilyama Extension Mine; Pioneer Mine; Little Emma Mine; Lilyama Copper and Gold Mine; Volo Mine), Pilot Hill, Pilot Hill Mining District, El Dorado County, California, USAi

Regional Level Types
Pioneer-Lilyama Mine (Lilyama Mine; Lilyama Extension Mine; Pioneer Mine; Little Emma Mine; Lilyama Copper and Gold Mine; Volo Mine)	Mine
Pilot Hill	Hill
Pilot Hill Mining District	Mining District
El Dorado County	County
California	State
USA	Country

A Cu-Au-Ag-Fe-W mine located in the W½SW¼ near the _W¼ corner of sec. 3 (Lilyama), T11N, R9E (MDM), 4.1 km (2.5 miles) E of Pilot Hill (town), W of Greenwood Creek and N of Hastings Creek, on private (patented) land. Discovered in/before 1870. The Pioneer Mine is about 2,000 feet from the Lilyama. Logan (1938) shows the Pioneer as an unpatented claim of 20.65 acres. Owned by the Lilyama Copper-Gold Mining Company, California (1978); Morning Star Mining Corp., California (1977). Operated by Wilcox-Lilyama Mining Company (F.R. Wicks, Manager). This deposit was worked as 2 separate mines in the 1860's. The main Cu deposit was discovered during the period 1889 to 1890. The mine was rehabilitated in 1955. Produced during the period 1944 to 1946. MRDS database stated accuracy for this location is 10 meters. In 1957, this mine produced all of the county's recoverable Cu and appreciable amounts of Au & Ag.

Mineralization is hosted in hornfels. The ore body forms pods, strikes N00E and dips 00E at a thickness of 12 meters, depth-to-top of 10 meters, width of 18 meters and/or 30.48 meters, and a length of 366 meters. Ore body No. 1 is a pipelike fissure vein and ore body No. 2 is breccia fill. The most widespread rock in the stock is a medium- to coarse-grained hornblende granodiorite. A lighter colored facies of granodiorite, nearly devoid of mafic minerals, underlies a large area of the mines. Syenite porphyry is present as a narrow dike intruding hornfels in the lower tunnel of the Lilyama Mine. The adit also exposes an irregular dike of dark hornblense diorite which is penetrated by stringers of granodiorite. The most prevalent metamorphic rock is the fine-grained hornfels, light gray-green to black, and locally containing large biotite flakes. A garnet quartzite with a fine-grained saccharoidal texture crops out directly above the ilyama Mine workings. At the Pioneer Mine, a coasely crystalline white marble is the important rock type. It trends slightly W of N, dips nearly vertically, and is not continuous. Tactite pods occur which range in size from small pods to those 100 or more feet in width. The sulfides occur as irregular masses or veinlets and are associated with abundant euhedral magnetite crystals. The ore bodies are those parts of the tactite that contasin commercial amounts of chalcopyrite and bornite. The primary mode of origin was hydrothermal activity and the secondary mode was contact metasomatism. Primary ore control was fracturing and the secondary control was faulting. Wallrock alteration is intense (carbonate silic.). Associated rocks include diorite. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains).

Local geologic structures include faults and joints: In the Lilyama area, member faults trend approximately E and dip 42-65S, with apparent displacements of less than 5 feet.

Workings include surface and underground openings with an overall depth of 40.23 meters. The Lilyama Mine has 4 adits with a total length greater than 1,000 feet, developed through a vertical range of 132 feet,and are not connected underground. The Pioneer Mine has 4 shafts and an adit. Of these only one 80 foot shaft and a short crosscut were accessible.

Production data are found in: Cox, M.W., et al (1948): 44.

Production statistics: Year: 1946 (period: 1946); material: ore; accuracy: accurate; average of ^2.5% Cu (3 weight percent).

Some ore was produced and stockpiled awaiting completion of work on a mill in 1955. Production table figures are from the Lilyama Mine.

Other Databases

Link to USGS MRDS:	10029708

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References