Geo 730: Jan. 16, Day 381: Patrick Creek Serpentinite

The rock here was first described to me as "tectonized harzburgite," which at the time was utterly opaque. My understanding of the classification of ultramafic rocks, other than dunite, is still pretty muddy, but I grasped pretty quickly that "tectonized" is simply an adjective meaning that the rock has been sheared and crushed beyond recognition. So the fact that it was once a harzburgite is kind of beside the point; it mostly isn't anymore. Due to hydration/alteration of the Mg-rich minerals- olivine in particular- the rock as a whole can now be described as serpentinite. Finding samples in which the harzburgite is apparent is possible, but it requires purposeful effort. I have posted on this outcrop before, in a broader discussion of serpentine.

Photo unmodified. May 8, 2013. FlashEarth Location. Indexed