Every year we look forward to visiting one of the most beautiful places in the world, the San Rafael Swell, a series of sandstone, shale and limestone that has been worn down by erosion by water, air and time.
One of the best things is that the collecting locations are fairly close to highway 70, a road we travel every year in order to go back and forth from California to Colorado for the annual Denver Mineral Show, which is taking place as I type this.
For rockhounds and lapidary artists, the bountiful red/yellow jasper found in this area is worth stopping for. The jasper nuggets are found with a bubbly rind, colors caused by iron oxides, accepting a fine polish.
There are several areas to collect jasper, as you can see on this map, the two main areas are directly south of I-70, both accessible with a standard passenger vehicle. The first location is just north of a dirt road you enter heading West, .7 mile from the exit on route 24. The next location is on a dirt road heading east 4.2 miles from I-70, or 3.5 miles from the first dirt road.
The exciting thing to find while out looking for jasper are thin walled geodes with crystals of celestite, calcite and quartz inside. By gently splitting along the cracks in the walls of the geodes, you can find bright blue crystals of celestite, up to 4.5 cm, along with calcite in various forms and colors and druzy quartz, sometimes with an amethystine color.
The geodes are created due to the fact that they were originally filled with anhydrite, which then dissolved, mixed along with the marine sediments, giving the proper environment for celestite to form. The celestite in this area used to be mined commercially back when celestite was in demand. Now, there is very little demand for the raw material, which can be sourced very cheaply from sources around the world. The celesite is now mined for mineral specimens, sporadically.
When looking for these jasper geodes, you can often tell if there are crystals inside by the weight. Be careful not to shake the geodes violently, as loose crystals can smack into the crystals attached on the matrix. You most certainly do not want to smash these geodes open with a hammer, you can typically find a crack or fissure in the wall and pry it open with a screwdriver.
Utah is a beautiful place. This remote, yet, heavily traveled, area of the world, is a perfect reason to stop and stretch your legs! I hope you enjoy a trip to this area at least once in your life!
We highly suggest this issue of Rocks & Minerals photographed above. Rocks & Minerals is well worth subscribing to, they are one of the best mineral magazines ever printed.