For those not tuned in to Southwest Geology, a sill is an igneous intrusive that has inserted itself parallel to the surrounding strata (a dike runs at angles to the strata). Palisade Sill is a huge intrusive in northern New Mexico between Raton and Taos on Highway 64. You won’t miss it when you head west into the canyon out of Cimarron. The sill is made of Monzonite, which is on the continuum between syenite (very light in color) and diorite (medium in color) and has plagioclase and orthoclase feldspars in approximately equal amounts. In short, it is a lighter than granite, but generally similar.
My favorite aspect of this imposing formation is that the joint systems are at nearly right angles, which leaves enormous faces and a ragged, blocky crest at the skyline. And, of course, lots of rubble along the stream below. Here are some images of the crestline.