Glass Mountain

Glass Mountain is an exposed mound of selenite, the clear crystalline form of gypsum, rising about 15 feet from the floor of Lower Cathedral Valley. Its pale crystals look striking beside the area's red sandstone towers, and the deposit is unusual for both the size of its crystals and how much sits in one place. I'd include it with the Temples of the Sun and Moon; the remote drive is the commitment, not the time spent at this one feature.

From UT-24, take the Lower Cathedral Valley turnoff west of Caineville; it's easy to miss. Follow the road north about 18 miles to the valley junction, then take the northeast branch for Glass Mountain. The dirt roads are rough and remote. High clearance is strongly advised; four-wheel drive may be needed, and recent rain or snow can make the route impassable. The full 57.6-mile loop takes six to eight hours, and the Hartnet approach includes an unbridged Fremont River crossing. Check road and ford conditions before leaving. There is no potable water in Cathedral Valley, and cell reception is usually poor or absent.

The name is a little misleading: this isn't volcanic glass. The mound is gypsum in its selenite crystal form, estimated at about 15 feet high. Explanations differ on the underground process: one describes groundwater concentrating dissolved gypsum into a plug in the Entrada sandstone; another traces the mineral to Jurassic seas and says it moved upward along fractures. Erosion exposed the deposit, while erosion of the surrounding red sandstone helped shape the valley's free-standing towers.

Collecting rock or minerals in the park is prohibited. For a photo, put the crystal mound in the foreground with Temple of the Sun behind it. That shows both the unusual deposit and the sandstone tower that makes its setting unmistakable.