Different types of phosphate deposits and different sources of phosphate in the United States are briefly discussed. In Florida two types of phosphate are now mined, land pebble and hard rock. The principal characteristics of these types of rock are stated and methods of prospecting, mining and recovery briefly outlined. Testimony given before the Congressional Committee to Investigate the Adequacy and Use of Phosphate Resources of the United States, November 28, 1938, at Lakeland, Fla., showed Florida's reserves to be far greater than previously supposed. Similarly at corresponding hearings in Tennessee a few days earlier the reserves of brown phosphate, the only type now mined in that State, were shown to exceed earlier official estimates. Reserves of the Western fields have been raised a little to bring them abreast of current information but no attempt has been made, as in the other States named, to include lower grades of rock than those formerly considered in the estimates. Professor J. Stewart Williams has shown for Utah that such a procedure would tremendously increase these figures.
Reserves of the United States as a whole are now considered to exceed ten billion tons, not counting those classed as possible or certain phosphatic limestones mentioned at the hearings of the Congressional Committee. As nearly 2,000,000 acres of public land in the Western States and 66,000 acres in Florida remain to be examined for their phosphate content the stated figure will ultimately be greatly increased. At the present rate of consumption, 3,000,000 tons annually, ten billion tons would last more than 3,000 years.
