5.2: UM1 Soapstone and Serpentinite
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Outcrop and Hand Sample Photos and Videos
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.
Thin Section Photos and Videos
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.