By: shelley-jaye
Image: Credit: Robin Rohrback, Mid-Atlantic Geo-Image Collection (M.A.G.I.C.) on GigaPan. CC BY Attribution 3.0 ⧉
License: Creative Commons Attribution ⧉

Uploaded: 6 Jan 2020
Last Updated: 15 Jan 2020

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The sheet silicate mineral biotite. The color indicates that Fe and/or Mg exists in the mineral's chemistry. Note that one thin sheet of dark colored biotite can be virtually colorless. The ability to separate into thin sheets is described as the mineral's cleavage.