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Blend of feldspar +‎ silica, +‎ -ic.


felsic (comparative more felsic, superlative most felsic)

  1. (mineralogy) Enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium.
    • 1954, J. C. Olson, D. R. Shawe, L. C. Pray, W. N. Sharp, Rare-Earth Mineral Deposits of the Mountain Pass District, San Bernadino County, California, U.S. Geological Survey Professional Paper 261, U.S. Department of the Interior, page 22,
      Much of the southern half of the southeastern body is a mafic syenite, slightly more felsic than the shonkinite.
    • 1983, Paul C. Bateman, A summary of critical relations in the central part of Sierra Nevada batholith, California, U.S.A., J. A. Roddick (editor), Circum-Pacific Plutonic Terranes, Geological Society of America Memoir 159, page 241,
      Within comagmatic suites, successively younger granitoids are commonly, but not invariably, more felsic, representing progressively lower temperature mineral assemblages.
    • 1992, David C. Champion, Bruce W. Chappell, Petrogenesis of felsic I-type granites: an example from northern Queensland, P. E. Brown, B. W. Chappell (editors), The Second Hutton Symposium on the Origin of Granites and Related Rocks, Proceedings, Geological Society of America Special Paper 272, [Originally published in Transactions of the Royal Society of Edinburgh: Earth Sciences, Volume 83], page 115,
      The Claret Creek Supersuite granites are a little more felsic (65-77% ), and are chemically distinctive, having higher , , and , and lower , , and than the granites of the Almaden Supersuite.


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felsic (plural felsics)

  1. A rock with such properties.
    • 1953, R. C. Emmons, Chapter 6: Petrogeny of the Syenites and Nepheline Syenites of Central Wisconsin, R. C. Emmons (editor), Selected Petrogenic Relationships of Plagioclase, Geological Society of America Memoir 52, page 80,
      The central part of this nepheline syenite is very white felsics with black mafics in it. The entire area contains many nepheline-bearing dike rocks, but almost all are gray or pink or even red due to the color in the felsics.
    • 1992, T. E. Smith, Chapter 1: Volcanic Rocks of Early Proterozoic Greenstone Belts, K. C. Condie (editor), Proterozoic Crustal Evolution, Elsevier, page 35,
      There are also calcalkaline felsics that have highly enriched LREE[light rare-earth element] patterns with lower overall abundances.