Episyenites in the Sevilleta National Wildlife Refuge, Socorro County, New Mexico: preliminary results
— Virginia T. McLemore

Brick-red episyenites are found in an outlier of Proterozoic-age rocks on the Sevilleta National Wildlife Refuge in central New Mexico. The term episyenite is used to describe altered rocks that were desilicified and metasomatized by alkali-rich fluids. Similar episyenites are found elsewhere in New Mexico and southern Colorado and are thought to be part of a Cambrian-Ordovician magmatic event that is documented throughout southern Colorado and New Mexico. Unlike episyenites in the Caballo and Burro Mountains, which contains moderate to high concentrations of rare earth elements (REE), uranium, and thorium; the episyenites in the Sevilleta National Wildlife Refuge have no economic potential.