Thursday, December 13, 2012

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...

7 comments:

coconino said...

Pretty. I'll have to see if we can wind our way through there this coming summer on our way to MT in June.

Silver Fox said...

It would be great to meet you, if you have a chance to come through!

coconino said...

Ditto! I'm pushing the SO to bring the Mange-y Rangie, so we can have serious adventures en route.

Silver Fox said...

Sounds like a fun trip. I should be working near the area where these photos are from, plenty of good off-roading around.

thefarmerlady@msn.com said...

Wow!!! Bingo : )
I have been working on figuring this out for EVER!!! and here it is!!!! Thank YOU!!I am in Maine on a little farm and have been researching the Rocks here and this is one of them!!!! : ) Sorry just a little excited....
I think the other mineral my be Andalucite, I think I also found Paragonite shist in mix too, I still have many more to nail down.Its amazing how totally different after they have been properly cleaned, I like you marvel at its history and make up

Silver Fox said...

Sounds like you know a great place to go rock collecting!

Anonymous said...

Yes! My yard! basement crawl space, I am lucky enough to rockhound all year long at home : )