Collecting Fluorescent Rocks at the
White Knob Quarry
 

On a very hot Saturday afternoon, our group assembled at the White Knob Quarry in the Lucerne Valley of California.  Even though the thermometer registered 103 degrees F, we decided to brave the dry heat and possible wind to be able to collect something new to our group.  Each year as we visit the San Diego County Fair at Del Mar, we ooh and aah over the darkroom presentation of fluorescent minerals from all over the world.  The colors are both weird and spectacular at the same time, especially the green rocks with the red spots from the lead mines at  Franklin, New Jersey.  So, when an opportunity to join a collecting trip for fluorescents was offered to us by Diane Rose, the field trip coordinator for the Fallbrook Gem and Mineral Society, we jumped at the chance.  One of the advantages of belonging to a lapidary club is the possibility of getting into a location only available to large, organized groups.  The White Knob limestone quarry, owned by the worldwide company OMYA, is one of these restricted locales.  While the main focus of the operation is to mine high grade calcium carbonate for the food and pharmaceutical industries, it also produces a number of fluorescent minerals.  The opportunity to collect these special minerals with the aid of a company geologist is offered as a community service to clubs such as the Boy Scouts and gem and mineral/lapidary clubs.

We caravanned together  up the freeway to the high desert of Lucerne Valley, arriving at the company's production  facility located 1000 feet below the quarry.  First we met with the staff geologist, Mr. Howard Brown, who showed us samples of the rocks we would be collecting, then gave a short presentation of the quarry operations and the geology of the limestone deposits in the surrounding San Bernardino Mountains.  We then proceeded to our vehicles where, after a short stop to view the large transport trucks, we continued on to the first stop at the quarry itself.  The huge piles of  pure white calcium carbonate (calcite) glistened in the afternoon sun, looking rather like granulated sugar.  At this stop, Howard pointed out the contact zones, where the calcite was intruded into the native granite.  This would be the area to search for the fluorescent minerals such as pink and blue calcite, wollastonite, epidote, sphalerite, caliche, and  aragonite.  Then, he led us to the next collecting area, where the quarry workers had piled tons of material for us to choose from.  There was some lovely yard rock composed of alternating stripes of pink calcite, green epidote, and deeper pink rhodonite spotted with some nice purple garnets (microscopic), which we couldn't help but load into the truck. 

After our afternoon collecting (heat not too bad with lots of PowerAde and water to drink), we stayed for a tailgate picnic, waiting for the next group to join us for the night collecting experience.  Several members of the Fluorescent Mineral Society brought their powerful battery powered UV shortwave/long wave lights to make the rocks glow.  We soon realized how almost useless small portable lights were, compared to their powerful ones---we were glad they were generous enough to help us view our potential finds plus handing us some great rocks to take home.  That is one of the best things about people in the rockhounding circle--that generosity with sharing knowledge, techniques, collecting sites and rocks enough for everyone. 

An added bonus this trip was the chance to ask Mr. Brown all the questions we could think of, not to mention all the great specimens he gifted us with throughout the day.  Without the benefit of his knowledge, we would have not fully appreciated the rare experience of this most enjoyable and productive collecting day.  Now, we just have to build ourselves a good viewing box and acquire better and brighter UV lights to continue to fully enjoy our glowing rock collection.  Let's just say that from now on, we will be sure and plan our trips around fluorescents as well as turquoise, fossils, fire agate, and all the rest of the goodies out there just waiting for us!