6 BULLETIN" 312, U. S. DEPARTMENT OP AGRICULTURE. 



thickness of about 1 foot and are mined by means of grab buckets or 

 clam-shell dippers. 



The rock as a whole consists of gray nodules of medium hardness, 

 frequently much pitted and the holes filled with clay or calcareous 

 mud, which must be removed by a washing process. 



The average grade of the marketed product is about 61 per cent 

 tricalcium phosphate. The average cost of producing South Caro- 

 lina phosphate is not far from $3.46 per ton, including interest, 

 overhead, etc., and the rock, on board cars at the mines, brings about 

 $4 per ton. 



Since the discovery of the higher grade and more cheaply mined 

 phosphates in Florida and Tennessee, the exploitation of South 

 Carolina rock has gradually fallen off. Most of the rock now mined 

 is consumed locally for the manufacture of acid phosphate and 

 double acid phosphate. The latter product, being very rich in 

 soluble phosphates; will stand the cost of transportation. 



THE WESTERN PHOSPHATES. 



The western phosphate fields are located in southeastern Idaho, 

 western Wyoming, northern Utah, and western Montana. The 

 regions in which the phosphate has been mined or developed so far lie 

 in southeastern Idaho, near the little towns of Soda Springs, George- 

 town, and Montpelier on the Oregon Short Line Railroad; along the 

 western front of the Sublette Mountain Range, near Border Station 

 on the Idaho-Wyoming border; at the south end of this same moun- 

 tain range, about 1 \ miles from Cokeville, Wyo., which is also on the 

 Oregon Short Line Railroad; and in the Beckwith Hills in southwest- 

 ern Wyoming and in northern Utah along the western front of the 

 Crawford Mountains, about 5 miles from Sage Station, Wyo. Practi- 

 cally no development work has been done in Montana, but the 

 phosphate has been recognized near Melrose, Mont., a town on the 

 Oregon Short Line Railroad, and also at Garrison, Philipsburg, and 

 Cardwell on the Northern Pacific Railway from 40 to 70 miles north 

 of Melrose. 



The topography of much of the phosphate area is extremely rugged, 

 but many of the beds of phosphate are readily accessible and within 

 easy reach of the railroads mentioned or possible spurs from them. 



The western phosphates are original sedimentary deposits laid down 

 when that portion of the earth's surface was submerged in water. 

 The rock is of Carboniferous age and occurs in beds from 2 to 6 feet 

 thick, overlain by limestone and phosphatic shales.* It ranges in 

 color from light gray to jet black and in texture from a readily 

 crushed, coarsely oolitic material to a hard massive rock difficult to 

 crush. The rock varies in its phosphate content from 65 to 75 per 



