PEBBLE PHOSPHATE DEPOSITS. 
43 
and casts of shell. The phosphate rock presents no regularity or 
uniformity in size or form and from the same matrix may be washed 
pieces varying from i mm. or less to 50 mm. or more in diameter, 
or in weight from a few milligrams to several ounces. The larger 
pieces when examined under a lens are usually found to contain 
grains of sand, small phosphate pebbles and casts of shells imbedded 
in a matrix of nearly uniform texture. The small phosphate pebbles 
are often well rounded. 
In color the phosphate rock is likewise variable. Some of the 
pieces are white, while others are tinged with yellow, cream colored, 
brown, amber colored, gray and black. A few of the pebbles, es¬ 
pecially the smaller ones, are of uniform texture throughout. With 
many of the pebbles, however, the outer layers are more compact 
and probably more highly phosphatized than is the interior. 
Analysis of phosphate pebbles washed from the phosphate bed at the mine 
of the Pierce Phosphate Company, Pierce, Florida. Air-dried sample. 
Moisture -1.81 
Insoluble matter, sand, etc.-6.62 
Phosphoric acid, 30.67, equivalent to tri-calcium phosphate-66.98 
Iron and alumina- 1.32 
Calcium oxide, 3.05, equivalent to calcium carbonate_6.94 
Analysis of phosphate pebbles washed from the phosphate bed at the mine 
of the Prairie Pebble Phosphate Company near Mulberry, Florida. Air-dried 
sample. 
Moisture -1.33 
Insoluble matter, sand, etc.-6.87 
Phosphoric acid 35.34, equivalent to tri-calcium phosphate-77.18 
Iron and alumina_:-'.-0.93 
Calcium oxide, 1.39, equivalent to calcium carbonate_3.16 
Analysis of phosphate pebbles washed from the phosphate bed at the mine 
of the Phosphate Mining Company, near Mulberry, Florida. Air-dried sample. 
Moisture - 3.22 
Insoluble matter, sand, etc--- .35 
* Phosphoric acid 34.73, equivalent to tlri-calcium phosphate—-75.85 
Iron and alumina___0.28 
Calcium oxide, 3.73, equivalent to calcium carbonate_8.49 
The matrix in which the phosphate pebbles are imbedded in¬ 
cludes chiefly sand, clay, corals, rock fragments, flint pebbles, fossil 
bones, shells and petrified wood. The following analysis is of the 
matrix including the phosphate pebbles. 
