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| Top of Mosquito Pass used by stagecoaches long ago |
Just west of Mosquito Pass and east of Leadville, Colorado
is a fairly well known area for finding twinned orthoclase crystals. I had been
to this site many years ago on a club field trip and thought it might make for
an interesting diversion to an All Terrain Vehicle (ATV) trip my digging
partner had planned. While orthoclase crystals don’t excite
me too much, the fact that many of the crystals are penetration twins (Carlsbad) makes them
desirable for the mineral collector.
http://www.uta.edu/faculty/mattioli/geol_3313/Feldspar_Twinning.pdf
We drove through Fairplay, CO, parked the
vehicle and headed up the east side of the pass on ATVs. The visibility was
somewhat restricted due to fires in western Washington, Idaho and Montana, but better than the
last few days. There were many things to see including wildlife, abandoned
mines and friendly people along the 4-wheel drive road.
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| Marmot warming up |
As we crested the pass my foggy memory cleared of where the exact crystal site was and we motored down the pass quickly reaching the old dig site. I reread some material by Voynick, 1995, Colorado Rockhounding to help refresh my memory of the location. The twinned orthoclase crystals can be found in quartz monzonite
porphyry outcrops. Near the digs you can see host rock with the orthoclase
crystal indentations in them. The ground was also scattered with what
appeared to be pea-size or smaller octahedral quartz crystals that had
weathered out of the host rock. We dug into the side of an old dig and found the occasional crystal weathered out of it's host rock. No pockets of crystals here, but time and a little determination yielded results.
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| Digging area |
We only spent a little over an hour at the site
but did find a few collectible crystals. I read that Carlsbad twinned orthoclase
crystals up to 2” can be found so after finding one double terminated crystals
of 3” I figured I could do no better and it was time to continue our ATV fun. My
digging partner generously provided the transportation and made for a very
enjoyable day. This particular site is more easily accessed by 4-wheel drive
vehicle from Leadville but either way you go to this 12,000Ft dig site be
mindful of your 4-wheel abilities, altitude and the changeable weather.
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| Some dendritic manganese patterns on the crystals |
