Sunday, May 18, 2014

Geo 730: May 18, Day 504: Patchy Blue Amphibole

Here we see a fairly common phenomenon in sheared coarse metamorphic rocks: a tendency to segregate into separate groups. I don't entirely understand this; it certainly isn't based on something as simple as color, though it can appear to have that effect. It's more likely due to some physical characteristic like susceptibility to plastic deformation. In this case, more plastic mineral groups such as chlorite end up somewhat segregated from less plastic minerals, like the glaucophane. Also, if you enlarge the photo to full-size, you can spot bright little red garnets all over the place, though for me, at least, they tend to stand out better from the lighter micaceous matrix.

Photo unmodified. March 9, 2012. FlashEarth location.

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