Today, I took a trip to a mountain called Jelm about an hour southwest of Laramie.  Man what a mountain!  So many different things going on it’s difficult to know where to start!

So let’s start at the beginning.  I’ve wanted to go to Jelm ever since I saw samples of schist with lovely garnet phenocrysts in them.  After a long, hard winter of not being able to rockhound, I finally get my opportunity and what better place to go than here.

Upon arrival my friend, Mitch, and I checked out a blasted mine of presumably copper.  Chrysocolla (one of a few copper oxides) was everywhere in this spot!  But, we decided to press on to the schists as to not overfill our packs at that time.

So we scuttled along the slope of the mountain, all the while stopping to observe the unique metamorphic geology of Jelm.  We reached the are where the garnet schists were coming off of the parent rock and boy what a treat!  So much garnet, we were tempted to take half the mountain with us!  Instead, we settled on a few choice samples, mine of which you can see in the first two photos.

One interesting feature of the area was the HUGE epidote veins in the schists.  I mean, these things were as big as my arm!  The big green rock pictured is one such sample from the area.  I didn’t take it directly from the veins itself, I found this one laying on the mountainside.  Lucky me!  The photo after it shows another group of epidote inside 

Pressing onward we saw so many more garnet schists that we just had to look around the area some more.  All of this being uphill up a talus slope; it was pretty complicated maneuvering, but we managed.  Many of the schist facies were penetrated by quartz intrusions and it was around these intrusions that we found lots of mica (both bio and musc) which was curious.  I have a sample of that in the 5th photo.

The sixth photo is something I’m really proud of finding.  In this rock are isoclinal folding, a fault, AND a large garnet phenocryst.  Not something you get to see every day!  Mitch was jealous, but there were many times when I was jealous of his finds too.

Finally, we headed back to the car, hiking up and around the schist outcrop.  We ended up right back in the chrysocolla area so we decided now was a good time to take samples.  The last 4 photos are all from that area.  The third to last photo suggests the presence of malachite in the rock, and the last photo is a sample of goethite!  I never thought I’d ever find one in the wild, but I did and it’s such a good sample too!  We broke open a yellow rock (odd for the chrysocolla bearing rocks) and found it along with a few other samples.

Man what a trip.  Can’t wait to go back again!

EDIT: The mineral we thought was goethite is actually limonite!  

  1. mikespader posted this