Today we will be off to hunt for more “Pecos Diamonds” in the Roswell area. Although we can’t prospect in the park, there are several collecting sites within 10 miles or so that are listed in scientific papers and rockhounding books. We have already had good luck while hunting on BLM land in the Artesia area.
In a nutshell (just in case you don’t have time to read an 11-page paper), “Pecos Diamonds” are not real diamonds, but rather are double terminated quartz crystals that occur in a wide variety of crystal forms and crystal clusters. They can be found here and there along the flood plain on the east side of the Pecos River in New Mexico, from Artesia north for about 100 miles or so. They form in massive alabaster found in the Permian “Seven Rivers” formation, in the back reef section of the Guadalupe Reef Complex, The crystals themselves probably formed in a slushy silicon dioxide and calcium sulfate mixture, with the crystals forming from the silicon dioxide (+ impurities for color) and the calcium sulfate hardening into alabaster (a fine-grained gypsum).
We actually found some of the crystals still in matrix in the gypsum – but that is unusual. The crystals fall out easily and are typically found just lying around on the ground. Colors can range from clear to black, but most of the ones we found were yellowish through orange and red.