Theme and Variations on Anorthosite and Labradorescence

Without a doubt, Siim Sepp‘s Sandatlas has already become one of my favorite new geoblogs. Back in the early heyday of geoblogging in 2007 it was a regular occurrence for the handful of geoblogers to highlight new geoblogs when they were discovered, and that’s something I’d like to get back into the habit of doing. Another thing that I really enjoyed in those days was when fresh geomemes would spontaneously appear and race through the geoblogosphere. It didn’t take much – an interesting post with a geologic theme that other geobloggers could echo with new variations. To some degree this sort of thing has been absorbed into the Accretionary Wedge, but often the Wedge format is too slow and cumbersome for a geomeme that ought to spread like wildfire. And so, when I saw Siim’s post about “Anorthosite and Labradorescence”this morning I knew I didn’t want to wait around for somebody to formalize this and turn it into a Wedge installment – I just wanted to post my reply right away.

And, of course, my reply comes in the form of a GigaPan three GigaPans that I shot this past August in the Adirondack Mountains of upstate New York. Back in early 2010 while I was doing a daily deskcrop/outcrop series on this blog, my ninth installment in that series was a series of photos of a roadcut along NY state highway 3 – the “Anorthosite Highway”. Those photos highlighted anorthosite and its labradorescence in its natural habitat, and, in many ways, they were the immediate precursor to my GigaPanning. Ever since I first got started using Google Earth I’ve wanted to recreate virtual field experiences through immersive photographic techniques. This began with basic panoramic photography and QTVRs and eventually came to fruition with GigaPans. Even so, GigaPans still have their own limitations. The series of GigaPans you see below would ideally be seamlessly nested into a single zoomable sequence, taking one all the way from the outcrop scale (top) to the macro scale (bottom). Unfortunately, there’s still no way to seamlessly merge GigaPan views together – at least, not yet…

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There are actually lots of interesting things to see when one zooms in on these GigaPans. The focus on the Wide view is not crisp at full zoom, though one can still make out cleavage reflections on large plagioclase laths in that view. Berti and Edi stand in in the outcrop Detail view to give a sense of scale (Edi is about 10cm tall). Finally, in the Macro view one can make out many details of the mineralogy only hinted at in the previous two views. In addition to the labradorescence (or opalescence, as it’s sometimes referred to in the Adirondacks), there are some nice garnet coronas between plagioclase and pyroxene crystals to remind you that while these rocks have an igneous origin, they also experiences the joy of a good metamorphic episode in the granulite facies.

labradorescence
Two details from the macro GigaPan illustrating labradorescence (or opalescence).
Opalescence
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