Dumortierite at the Champion Mine, Nevada

Here we are, back at the lower workings of the Champion Mine, standing on the second wall, looking at a funny, corrugated outcrop. If I look at this outcrop with a tilted head, I might imagine a sideways, not-quite-upside-down Nevada with corrugations of the Basin and Range forming large-ish mountain ranges (or I might imagine caterpillars crawling).

Closeup of the corrugated outcrop.

Most of the outer edges of the corrugations are terminated by planar, thin rinds of fibrous, purplish-red dumortierite. I'm not really sure what created the shape of the corrugations, but I'm thinking that they might be structural in origin, combined with some incipient cavernous or spheroidal weathering.

Thin rinds of dumortierite on schistose, Triassic rhyolite.

Fibrous to bladed dumortierite up close.

The orientation of the fibers or crystals reminded me of the slickenlines one might see on a slickensided fault surface, but I didn't have time to really check out this possibility by taking a lot of orientations with my Brunton.

Dumortierite in irregular veins cutting the Rochester Rhyolite.

Veins and a vein breccia.

Nice vein of fibrous dumortierite.

I'll have some more photos of dumortierite and dumortierite-sericite schist later, and soon, we'll head up towards the upper Champion Mine workings.

To be continued...