Geo 730: August 18, Day 595: We're Golden

In the lower right, you can see the draw of this quarry for kids in particular, but adults as well. Pyrite (and perhaps small amounts of chalcopyrite, too) are disseminated throughout much of the rock, but can form nice patches, as well as aggregations of small cubes, along joints and fractures. If you look carefully, especially at the photo in full size, you'll spot pyrite across this entire surface. The evidence for chalcopyrite is that on slightly weathered surfaces one can often spot iridescent colors- purples, reds, greens, blues- which I've associated with copper sulfides, but not plain iron sulfides. I haven't seen anything as colorful as bornite, though. If there is actually any copper here, its concentration is low. On the other hand, a doctoral dissertation (3.7 MB PDF) completed when my interest in the area was intensifying suggests that this area is underlain by a copper porphyry deposit. So the fact that there may be some copper in the sulfides here wouldn't be a shock.

Photo unaltered. August 5, 2012. FlashEarth Location.