Tuff is rock formed from compressed volcanic ash.
This mountain is also known as 'Scarface' due to the tuff layer looking like a scar.

Apparently, the tuff layer was formed as a result of three cataclysmic volcanic eruptions
15-25 million years ago that created nearby Superstition Mountain and the mountains around it,
destroying everything for 100 miles around and depositing ash as far away as present day Arkansas.

Scene illuminated only by city light miles away reflected off cloud cover.

Photographed in the Sonoran Desert north of Mesa, Arizona USA.