Southern Black Hills pegmatites

Region Central, North Central
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Focus area includes Harney Peak granite and surrounding pegmatites and veins and shear zones that cut Precambrian metasedimentary rocks. Area encompasses beryl occurrences in MRDS.
Identified resources Historical production of beryllium (beryl), feldspar, and mica.
Production About 4,200 tons of beryl was produced from Black Hills pegmatites between 1879 and 1958. In 1943, 130 tons of beryl ore were produced, averaging 11.85% BeO.
Status Past mining.
Estimated resources A number of small pegmatites contain some beryl, but are not an important source of beryllium at this time.
Geologic maps Redden and DeWitt (2008), scale 1:100,000; Redden and others (2010), scale 1:24,000; Wilson and DeWitt (1995), scale 1:100,000; DeWitt and others (1986), scale 1:250,000; Martin and others (2004), scale 1:500,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures More than 22,000 pegmatites have been recognized in the area of the Harney Peak granite, many cutting surrounding metasedimentary rocks.
Deposits Helen Beryl (MRDS dep_id: 10104268), Elkhorn mine (MRDS dep_id: 10055780), Tin Mountain mine (MRDS dep_id: 10104256).
Evidence from mineral occurrences MRDS.
Geochemical evidence NURE stream sediment data in the Harney Peak area are enriched in Li and U, but sample density it too low to identify targets.
Geophysical evidence No data.
Evidence from other sources No data.
Comments Primary commodities at the Tin Mountain pegmatite mine (MRDS dep_id10104256) are cesium, lithium, feldspar, and mica.
Cover thickness and description Most pegmatites and veins exposed at the surface.
Authors Laurel G. Woodruff, Benjamin J. Drenth, Darren J. Johnson.
New data needs New geological mapping for areas not currently covered by 1:24,000 scale mapping, geochemical data.
Geologic mapping and modeling needs Recent detailed geologic mapping, some at 1:24,000 scale.
Geophysical survey and modeling needs Geophysical methods not useful for pegmatite deposits.
Digital elevation data needs Lidar adequate.