PEBBLE PHOSPHATE DEPOSITS. 
41 
Iron and alumina- 0.27 
Calcium oxide, 7.58, equivalent to calcium carbonate—- 17-24 
Analysis of phosphate pebble washed from the Alum Bluff marl near Lulu, 
Florida. Air dried sample. 
Moisture --1.84 
Insoluble matter, sand, etc.- 22.46 
Phosphoric acid, 26.93, equivalent to tri-calcium phosphate -- 58.82 
Iron and alumina-1_ 3.02 
Calcium oxide, 1.85, equivalent to calcium carbonate- 4.21 
Analysis of phosphate pebble washed from the phosphatic rna: 1 on Black 
Creek, Florida. Air dried sample. 
Moisture - .88 
Insoluble matter, sand, etc- 18.94 
Phosphoric acid, 24.45, equivalent to tri-calcium phosphate__ 53.40 
Iron and alumina_-_ 0.23 
Calcium oxide, 5.07, equivalent to calcium carbonate__ 11.53 
The matrix in which the pebble phosphate is imbedded, is pre¬ 
vailingly a light colored yellow or sandy phosphatic marl, varying 
in texture* from soft and granular to hard and compact. The sand 
consists of clear grains of quartz. The following is an analysis of a 
sample of this marl: 
Analysis of sample of the bed rock marl from pit No. 5 of the Phosphate 
Mining Company, near Mulberry, Florida. Air dried sample. 
Moisture -——--- 5.03 
Insoluble matter, sand, etc.-__ - 43-45 
Phosphoric acid 6.77, equivalent to tri-calcium phosphate__ 14-79 
Iron and alumina_:- 0.25 
Calcium oxide, 10.41, equivalent to calcium carbonate_ 23.64 
PLIOCENE. 
THE BONE VALLEY FORMATION 
The upper Oligocene in the land pebble phosphate section of 
southern Florida is succeeded by the Bone Valley formation which 
is of late Miocene or early Pliocene age, a part or all of the Miocene 
being absent in this part of the State. The lower member of this 
formation contains the land pebble phosphate beds. That part of 
the formation above the phosphate bed consists chiefly of gray phos¬ 
phatic sands, variable in thickness. At some localities owing to 
surface erosion they are almost entirely removed, although else¬ 
where they attain a thickness of thirty feet or more. As a rule the 
sands are but slightly indurated. Locally, however, they form a 
hard rock with innumerable small cavities which give a vesicular 
