FLORIDA STATE HORTICULTURAL SOCIETY. 
139 
phosphate. The plate rock phosphate 
now being mined near Anthony is includ¬ 
ed in this paper with the hard rock. The 
soft phosphate of which there is a con¬ 
siderable quantity intermixed with other 
phosphates is, under present methods of 
mining, unfortunately not recovered. 
The hard rock is a high-grade phos¬ 
phate. Most of it is sold under a guarantee 
that the entire shipment will average 77 
per cent, calcium phosphate (“bone phos¬ 
phate of lime;”) that iron and alumina 
combined will not exceed 3 per cent.; and 
that the moisture content will not exceed 
3 per cent. The hard rock which is now 
being mined occurs along the gulf side of 
the Florida peninsula from Suwannee 
and Columbia Counties on the north to 
Citrus and Ffernando Counties on the 
South. It lies in pockets of irregular oc¬ 
currence and extent and rests usually up¬ 
on limestone of Vicksburg (Lower Oli- 
gocene) age. 
The land pebble deposits are of Plio¬ 
cene age, and are less irregular in their 
manner of occurrence than are the hard 
rock phosphates. The chief land pebble 
region lies to the South of the hard rock 
region. The deposits being worked lie 
in Polk and Hillsboro Counties. Most of 
the land pebble is sold under a guarantee 
of 68 per cent calcium phosphate, iron 
and alumina not to exceed 3.5 per cent, 
to 4 per cent, and moisture not to exceed 
3 per cent. 
River pebble has been produced chiefly 
from Peace River and its. tributaries. The 
usual guarantee is 60 per cent, calcium 
phosphate; iron and alumina 3 per cent, 
and moisture 3 per cent. 
Phosphates varying in quality and in 
quantity, mostly low-grade and at pres¬ 
ent undeveloped are found at numerous 
other localities in Florida from the Apa¬ 
lachicola River on the West to Lee Coun¬ 
ty on the South. 
The production of river pebble, the 
first of the Florida phosphates mined, in¬ 
creased gradually from 1888 to 1893 
when the maximum production of 122,- 
820 tons was reached. From the year 
1893 to the present time there has been 
with some fluctuations a decrease in the 
output of river pebble, the total for 1908 
being 32,950 tons. 
The discovery of hard rock phosphate 
was made soon after the beginning of 
mining of river pebble. The first ship¬ 
ment of hard rock was probably made in 
1890. The output of hard rock phos¬ 
phate has gradually increased from the 
beginning of mining to the present time. 
The total hard rock mined during 1908 
was 768,011 long tons, which is a con¬ 
siderable increase over the production of 
any previous year. 
The first shipment of land pebble was 
probably made in 1891, although develop¬ 
ment began somewhat earlier. In 1892 
the production amounted to 21,915 tons. 
The rate of increase of land pebble was 
at first gradual, but in late years has 
been very rapid. In 1906 the output of 
land pebble for the first time exceeded 
that of hard rock. The amount of land 
pebble mined during 1908 is greatly in 
excess of that mined during any preced¬ 
ing year, falling little if any short of 1,- 
150,000 tons. 
The total amount of phosphate mined 
in Florida during 1908 was 1,950,961 
long tons. At the present rate of in¬ 
crease Florida, five years hence, may be 
