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Comments on Gigapan: Anorthosite Roadcut (Macro)

Gigapan Comments (4)

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  1. Ron Schott

    Ron Schott (September 09, 2011, 08:23PM )

    I just added two shapshots to the wide view of this roadcut to show the contrasting colors of the weathered and fresh anorthosite: www.gigapan.org/gigapans/86445/

  2. Chris Fastie

    Chris Fastie (September 09, 2011, 02:35PM )

    OK, now I get it. That explains a lot. This geology is tricky stuff.

  3. Ron Schott

    Ron Schott (September 09, 2011, 12:55PM )

    It looks darker, but that's just because it's fresh (unweathered). Plagioclase in the labradorite compositional range has this blue color (with a bit of greenish from pyroxenes) but plag will weather to a whiter color. Thi color change causes something of a conondrum when explaining to students whether this is a mafic or felsic rock.

  4. Chris Fastie

    Chris Fastie (September 09, 2011, 08:06AM )

    This exposure seems to have a lot of dark minerals in it for anorthosite. Is that because there is less feldspar (which is often light colored) or because the feldspar is darker than at other places?