A deposit of phosphorite, estimated to be 11 feet thick, was found March 26, 1952, while the writer was mapping ancient sink fillings and collapse structures within the outcrop area of the Honeycut formation south of Marble Falls, Texas. The phosphorite is exposed in a road material pit on the eastern side of a Carboniferous outlier. It rests on shale typical of that in the Barnett formation of Mississippian age and is beneath spiculitic limestone at the base of the Pennsylvanian Marble Falls limestone.