United States.
—The principal deposits of phosphate rock in the United States are in Florida, South Carolina, Tennessee, Kentucky, Arkansas, Montana, Idaho, Wyoming, and Utah. Although by far the largest deposits are in the western states, those deposits yield less than 1 per cent. of the whole because of the lack of a large near-by market and because of high freight rates on the crude rock. It is not a matter of common knowledge, but it is, nevertheless, a fact, that the western rock phosphate deposits are so extensive as to be practically inexhaustible, even if the entire world depended on them for its supply of phosphate.
The Florida phosphate deposits, which are the most extensively developed in the United States, comprise three classes of phosphate—hard rock, land pebble, and river pebble. The first is highest grade, the second is produced in largest quantity, and the third is not mined at present. The hard-rock deposits lie in a narrow strip along the western part of the Florida peninsula from Suwanee County to Pasco County, a distance of approximately 100 miles. The land-pebble phosphate area, just east of Tampa, is about 30 miles long and 10 miles wide. Sales of Florida phosphate declined tremendously after 1913 through the restriction on exports by the war. In 1913 the sales were 2,500,000 tons, valued at $9,500,000, and in 1915 the production was 1,350,000 tons, valued at $3,700,000.
South Carolina produces land rock phosphate in the vicinity of Charleston. River-pebble phosphate occurs in the same area but is not mined. Some of the South Carolina output has been exported annually. Sales decreased from 169,000 tons in 1911 to 83,000 in 1915, and the value in the same years from $673,000 to $311,000.
Tennessee deposits of rock phosphate are in the west-central part and extreme northeast corner of the state; the latter have not been mined. Three types are recognized and known by their colors as brown, blue, and white rock; the last has not been mined recently. The brown rock is sold under guarantee of 70 to 80 per cent. tricalcium phosphate; the blue rock varies considerably in its phosphatic content. Sales of Tennessee phosphate in 1914 were 483,000 tons, valued at $1,823,000; by 1915 they had fallen to 390,000 tons, valued at $1,328,000.
Kentucky has been an insignificant producer of phosphate rock in recent years. Arkansas phosphate deposits are in the north-central part of the state. The output is small.
Four western states possess enormous deposits of high-grade rock phosphate, but their output is as yet insignificant, being only 3,000 to 5,000 tons a year. The producing states are Idaho, Utah, and Wyoming. Montana is not a producer, although it contains extensive deposits easy of access and close to rail transportation.
Idaho has an unlimited supply of high-grade phosphate in the southeast part of the state. A small quantity is mined in Bear Lake County. The Utah deposits are east of Great Salt Lake, in the Wasatch and Uintah ranges, and east of Bear Lake. These deposits are extensive, but the rock is leaner than the general run of the Idaho phosphate, averaging nearer 60 per cent. than 80 per cent. tricalcium phosphate. Western Wyoming also is rich in rock phosphate, the deposits being mostly in the Owl Creek, Wind River, Gros Ventre, and Salt River ranges. Some of the beds are thick, carrying 80 per cent. tricalcium phosphate, and extend for many miles. They constitute a reserve supply that may be called inexhaustible. Small local demand for fertilizer and lack of cheap transportation may retard for some years the development of the great and rich western deposits.
An estimate of the quantity of rock phosphate available in the United States was made several years ago and need not be revised to account for that mined in the meantime. It is repeated here:
Reserves of Phosphate Rock in the United States