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Show Bertrandite, Beryl and Other Economic Minerals of the, Grover Pegmatite Between, Denver and Idaho Springs, Colorado With a Discussion of Pegmatization as a By-Product of Granitization of Sediments Arthur L. Crawford? and Alfred M. Buranek" Location, History, Production The Grover pegmatite is located on North Beaver Brook, four townships west of Denver, Colorado, and south about two miles from the parallel passing through the center of Denver City. It was first prospected for its mica content many years ago; but it was not until 1937 that the pegmatite was opened as a Ield-' spar mine and shipments of feldspar, mica, and more recently beryl were made. Bertrandite was discovered in 1942 by the senior author while studying the paragenesis of the beryl and associated minerals. It occurs as a replacement of beryl crystals and since it was previously not recognized part of it has been sold as beryl and part of it has been discarded with the waste. The total tons of the various minerals produced and sold to date are as follows: ' 1937 1938 1939 1940 1941 1942 Total 100 900 idle worked 400 80 1480 but made no 20 25 68 , Feldspar Muscovite 23 shipments Beryl 6 P 94 Total production to the end of 1942__________________________________________________ 1557 tons Quartz waste plus "ore" 2900 tons : --- Geology In the vicinity of the Grover Pegmatite the oldest country rock has been tentatively correlated with the Idaho Springs form ation. This is the oldest member of the pre Cambrian series as defined by S. H. Ba1l5 in the Georgetown quadrangle, and forms the host rock into which the other formations were injected. Its type exposures are in, the hills surrounding Idaho Springs where biotite sillmanite schist, biotite schist, and quartz gneiss inclose "lenses" of silicate rocks ... ... ... . Geologist and Mineral Technologist, Department of Mining and Metal lurqical Research, Utah Engineering Experiment Station, University of Utah, Salt Lake City, Utah. 2Geologist, Department of Publicity and Industrial Development of the State of Utah. "Sorted and available at mine. "Total includes two tons of material distributed as samples. 6Ball, S. H. "The Economic Geology of the Georgetown Quadrangle," U. S. Geo!. Survey Prof. Paper 63. p. 37 (1908). Volume 21, Proceedings of the Utah of Sciences, Arts . - Academy 101 and Letters |
