Hunting peridot in southern New Mexico

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On Saturday, I traveled to Kilbourne Hole with two of my friends to search for olivine, the mineral that’s called peridot when it’s gem-quality. After several hours on U.S. 180, I-10 and numerous Doña Ana County roads (yea washboard!), we arrived at the southeastern rim of the crater:


Kilbourne Hole (like Hunt Hole several miles south) is a maar, or volcanic steam crater. It’s a fascinating place (almost 2 miles across) that’s literally in the middle of nowhere. I took the below photo standing on the rim of the crater as seen above (where the rim juts out from the left).

We were there, as I said, to find olivine. I traveled with Meredith (from work) and her boyfriend Joe, a mining engineer with Phelps Dodge. Joe’s dad tipped us off to Kilbourne Hole about two weeks ago, and we’ve been planning a trip since.

While olivine is an abundant mineral on earth, transparent peridot is much rarer. Deposits have been found near the Red Sea and in Pakistan, Arizona and, of course, southern New Mexico.

We did a fair amount of research before the trip, aided mostly by this “field trip” journal by Robert Drummond. We knew we were looking for olivine basalt, which Drummond called “bombs” of rock thrown from the crater during its explosive creation. One good whack of your rock hammer would reveal olivine inside such “bombs.”
The first part of our search was almost entirely fruitless. Too close to the road (and, it turns out, too close to the crater rim) we found no “bombs.” Only after walking some distance did we find what we sought: some fist-sized nodules begging to be whacked. While we were elated, all we found were olivine deposits that disintegrated into a fairly fine sand:

Olivine Bomb

After about 3 hours, with the sun westering, we decided to call it a day. On our way back to the SUV, we heard the dull engine of an airplane approach. I include this photo to give you an indication of just how large Kilbourne Hole truly is:


We’re planning to return, now that we know what to look for and where to begin our search. More photos later.

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