PHOSPHATE ROCK: UTILIZATION AS FERTILIZER. 5 
the only navigable stream convenient to the blue-rock fields, and 
this river has not been used for shipping the rock in recent years. 
The blue-rock phosphate, as its name implies, is a massive grayish- 
blue or black rock, composed of flattened ovules and the waterworn 
casts of phosphatic shells. It weathers on exposure to a rusty yellow. 
The beds vary from 1 foot to 4 feet in thickness and are overlain 
normally by massive blue-black shale. In some localities the blue 
rock directly overlies the brown phosphate, making the mining of the 
two types quite profitable. 
As a rule the blue rock is of lower grade than the brown, but its 
content of tricalcium phosphate varies all the way from 60 to 80 per 
cent, the average content being not far from 72 per cent. The oxides 
of iron and aluminum are as a rule less than 3 per cent. The cost of 
mining blue-rock phosphate is about $2.50 per ton. 
TENNESSEE WHITE-ROCK PHOSPHATE. 
The deposits of white-rock phosphates so far exploited lie in Perry 
and Decatur Counties, both east and west of the Tennessee River. 
Some of the deposits in Decatur County are not far from a branch of 
the Nashville, Chattanooga & St. Louis Railway at Parsons, Tenn., 
but the only ready means of transportation afforded the present mines 
in Perry County is the Tennessee River, which is from 4 to 6 miles 
distant. 
The white-rock phosphate is of secondary origin and is more recent 
than either the blue or brown phosphate. It resembles somewhat the 
hard-rock phosphate of Florida and some of it is fully as high grade. 
Picked samples contain as high as 85 to 90 per cent of tricalcium phos- 
phate, with only a small percentage of iron and aluminum oxides. In 
carload lots the rock will grade from 72 to 78 per cent tricalcium 
phosphate. 
Because of the irregularity of the deposits and the lack of adequate 
transportation facilities the white phosphates have been exploited 
only to avery limited extent. Itis doubtfulwhether these deposits will 
be extensively developed before the more accessible brown-rock and 
blue-rock fields have been depleted. No mining has been done in these 
regions in recent years, so that it is difficult to arrive at the actual 
cost of production. The average cost of producing white-rock phos- 
phate would probably be slightly more than that of mining blue-rock 
phosphate. 
SOUTH CAROLINA PHOSPHATE. 
The phosphate area of South Carolina lies along the coast in a belt 
which is in places fully 20 miles wide, extending from the Wando 
River in Charleston County to the proud River in Beaufort County. 
The rock is of Tertiary age and occurs as nodules and bowlders em- 
bedded in a matrix of sand and clay. The beds have an average 
