42 FLORIDA GEOLOGICAL SURVEY-SEVENTH ANNUAL REPORT. 
appearance to the mass. A sample of the rock of this kind was 
found to contain 15.56% phosphoric acid (equivalent to 33.97% 
tri-calcium phosphate). 
At the surface is found as a rule incoherent pale yellow sand, 
which although variable has an average thickness of five to ten feet. 
It seems probable that these loose surface sands are merely residual 
having been derived by disintegration from the phosphatic and for 
the most part slightly indurated sands beneath. 
Fig. 2.—View in the Pembroke mine of the Coronet Phosphate Company, 
showing the gray more or less indurated phosphatic sands which lie above the 
workable phosphate bed. The gradation of the phosphatic sand into the loose 
surface sand and soil may be seen in this view. 
Although variable from place to place the phosphate beds have 
an average thickness of from eight to twelve feet; the maximum 
thickness over considerable areas, is possibly from eighteen to twen¬ 
ty feet, although locally, owing to depressions in the bed rock the 
phosphate may be much thicker. 
The phosphate beds are more or less definitely stratified, the bed¬ 
ding planes being frequently continuous for the full length of the 
exposures in the pit, some of which are a half mile or more in extent. 
Elsewhere the stratification is irregular and cross bedding is evident. 
The phosphate in this formation consists of rounded, flattened or 
angular pieces of rock or pebble, together with fragments of bones, 
' 
