While I believe mushrooms belong in the Mount Rushmore of Disgusting Foods along with green beans, quinoa, and brown rice, this mushroom I like! Weathered granite formations like Mushroom Rock are created by erosion, the granite pebbles that break away spread across the surface of the desert (my shins had an unpleasant introduction to these pebbles early on after we moved here when I slipped just a little on a hike).
Boolie 
This is really cool! I live here in arizona and I’ve never been there. I will go there in the future.
It’s a lovely little formation and not too far from the start of the Marcus Landslide Trail which starts from the Tom’s Thumb Trailhead. There are other examples on the trail of one that has fallen over and one that has a crack at the base that will eventually fall. There’s a much larger example in Balanced Rock which can be reached from either the Brown’s Ranch or Granite Mountain Trailheads.