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Geosciences LibreTexts

5.2: UM1 Soapstone and Serpentinite

  • Page ID
    11148
  • Outcrop and Hand Sample Photos and Videos

    Click on the image to enlarge.

    This outcrop is on the appropriately named Soapstone Rd. It is next to a creek and a small house that (at least used to) contain many, many dogs.

    Can you see the very weak foliation of the rock in the 1st picture (best observed in the left side of the photo)?

    The “bumpy” texture seems to be due in part to the weathering of the inhomogeneous rock. If you watch the YouTube video of the hand sample, clasts of ultramafic rock (peridotite?) are surrounded by reaction rims of serpentine. The main rock contains talc (feels slippery), magnetite, serpentine, and chlorite.

    Thumbnail for the embedded element "UM1 Soapstone hand sample"

    A YouTube element has been excluded from this version of the text. You can view it online here: pb.libretexts.org/petrology/?p=369

    Thin Section Photos and Videos

    Click on the image to make it larger. 1st = plane polarized light; 2nd = cross-polarized light.

    Unfortunately, we don’t have a thin section of one of the ultramafic clasts. However, you can see some of the minerals in the main section of the rock here. At the top = lower interference colors and fibrous = serpentine minerals and chlorite. At the bottom, higher-order interference colors = talc. Magnetite is opaque.

    Entire thin section scan. 1st = ppl; 2nd = xpl. Click on the image to make it larger.

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