No, this is not a mineral, at least not a mineral as you might think of. This is solid water, also known as ice. As it developed in a little waterfall along the Trail (just turned around 90 degrees for better Flickr viewability).
Water, at least to the chemist, physicist and biologist, is one of if not the most complex and enigmatic substance on earth. Little wonder Mother Nature has used it liberally to prepare Life in her kitchen…