Silver Crater Mine, Faraday Township, Hastings County, Ontario, Canadai

Regional Level Types
Silver Crater Mine	Mine
Faraday Township	Township
Hastings County	County
Ontario	Province
Canada	Country

For a discussion on "betafite" from the locality, see https://www.mindat.org/mesg-315893.html

History
"Silver Crater Mines, Limited, was incorporated in February 1951, with an authorized capitalization of 3,000,000 shares of ftl par value, of which 2,543,215 have been issued. The head office is at 696 Yonge Street, Toronto. The mine address is Cobalt. The company owns the Silver Banner and Ophir properties and has a lease on the Mensilvo property, all in Coleman township, district of Timiskaming. It also holds claims in Faraday Township, Hastings County.

The Basin property of Silver Crater Mines, Limited, comprises lot 31, concession XV, Faraday Township, Hastings County. The property was acquired in 1953. It is about 8 miles (ca. 13 km) west of Bancroft and is accessible from the Monck road by a truck road 2 miles (3.22 km) long. Silver Crater Mines, Limited, is a wholly-owned subsidiary of International Cobalt and Silver Mining Company, Limited. In 1953-55 the company carried out exploration on a carbonate body containing crystals of betafite, a multiple oxide of niobium, titanium, and uranium. In 1925 the north end of the carbonate body was worked for black mica by S. Orser and D. J. Wilson, and from 1947 to 1949 the property was operated by Bancroft Mica and Stone Products Mining Syndicate, Limited, producing scrap and trimmed mica. This production all came from an open-pit, which, in 1949, was 30 feet (ca. 9 m) in diameter with a 65-foot wall against the slope of the hill, and a 12-foot wall on the outer side.

Silver Crater Mines, Limited, commenced operations in 1953 and explored the radioactive part of the carbonate body to the south of the old mica pit by a number of trenches and six shallow, X-ray drill-holes. The work was continued in 1954 by bulldozing overburden and weathered rock from the top of the carbonate body and by diamond-drilling. By the end of 1954, 14 inclined holes and 9 vertical holes, totalling 4,274 feet (ca. 1,303 m), had been drilled. Drilling was continued in 1955, 11 vertical holes being completed for a total footage of 1,339 feet (ca. 408 m). The carbonate body was also explored by an adit, the underground development amounting to 435 feet (ca. 133 m) of drifting and crosscutting and 94 feet (ca. 29 m) of raising. The property was inactive in the latter half of 1955." (ARV65)

Geology
The Silver Crater Mine accesses a crustal carbonatite that has intruded into biotite-amphibolite and syenitized gneiss. The property lies in a 0.75 mile (1.21 km) wide zone between a large domain of granite and hybrid granite gneiss to the north, flanked by marble and associated metasediments to the south. This zone consists mainly of syenite and syenite gneiss with lesser nepheline gneiss, and also contains small outcroppings of hornblende-plagioclase gneiss (ARV65). The carbonatite was most likely emplaced at ca. 1050 Ma during the late Ottawan stage of the Grenville orogenic cycle when ca. 1150 Ma lower crustal anorthosite-mangerite-charnockite-granite (AMCG) suite rocks underwent partial melting, resulting in the formation of highly evolved A-type granitic magmas (Emproto et al., 2020). Oxygen isotope data suggest that the Silver Crater Mine carbonatite was derived from the melting of local carbonate units during this magmatic event (Emproto et al., 2020).

The carbonatite mineralization consists primarily of calcite with lesser fluorite hosting phenocrystic apatite and betafite. Silicate minerals like hornblende, phlogopite, etc. occur primarily along the coarse silicate margins, but may also be found as floaters in the calcite. The Silver Crater Mine is most famous for its betafite crystals, which are an as yet unidentified member of the pyrochlore supergroup that is rich in Ca, U, Ti, and Nb. The crystals are entirely metamict from self-irradiation, so solving their crystal structure and understanding their original composition and site occupancies is not currently feasible (Emproto et al., 2020). It is a mystery where the Ti and Nb were sourced from when the carbonatite magma was formed (Emproto et al., 2020). These elements are very depleted in crustal carbonate rocks and are not considered to be mobile in the magmatic fluids that likely instigated partial melting of the local carbonate units.

Mindat Articles

Silver Crater Basin Property by Derek Nicol

Other Regions, Features and Areas containing this locality

References