Sericite

Sericite is the name given to very fine, ragged grains and aggregates of white (colourless) micas, typically made of muscovite, illite, or paragonite.[1] Sericite is produced by the alteration of orthoclase or plagioclase feldspars in areas that have been subjected to hydrothermal alteration typically associated with copper, tin, or other hydrothermal ore deposits. Sericite also occurs as the fine mica that gives the sheen to phyllite and schistose metamorphic rocks.

Not to be confused with Cerussite or lead carbonate.
A sample of sericite

The name comes from Latin sericus, meaning "silken" in reference to the location from which silk was first utilized, which in turn refers to the silky sheen of rocks with abundant sericite.

  • Sericite in thin section (fine, high birefringence flakes covering other larger minerals)
  • Granite in thin section under cross-polarized light in which feldspar crystals exhibit sericite alteration.
  • Staurolite-garnet schist in thin section under cross-polarized light with sericite.

References
  1. Nesse, William D. (2012). Introduction to mineralogy (2nd ed.). New York: Oxford University Press. ISBN 978-0199827381.


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