THE FLORIDA PHOSPHATE DEPOSITS. 
29 
dry mines and usually reach to the bottom of the phosphate 
formation in places encountering the limestone. 
In the southwestern part of Marion County and in Citrus 
County the hard rock phosphate-bearing formation reaches its 
maximum thickness. The underlying limestone dips in passing 
to the south, and is ordinarily encountered at a considerable depth 
from the surface. Many of the phosphate pits in this section 
are worked as dry mines to the underground water level and 
afterwards as dredge mines to such depth as the dipper will reach. 
Some of the pits on higher lands are mined as dry mines only. 
The pit at the Dunnellon Phosphate Company plant No. io 
was one of the first pits regularly worked in the phosphate section 
and has been continuously in operation for the past twenty years. 
This mine is operated by a dredge. The bottom of the phosphate 
is not reached in this pit and the full thickness of the formation 
at this place has not been determined. 
CITRUS COUNTY. 
The conditions in Citrus County are in a general way similar 
to the conditions in the' vicinity of Dunnellon in Marion County. 
The underlying limestone is only occasionally seen in the pits in 
this section. It is, however, frequently reached in the dredge 
operations below the water level. The surface of the limestone 
wherever seen projects as rounded peaks similar in character to 
the conditions further north. There is on an average more clay 
to be seen in the phosphate formation in this section than in the 
northern part of the field. In a few instances, notably that of 
the pit of the Istachatta Phosphate Company, the water level is 
within a few feet of the surface and the phosphate formation is 
entirely submerged. Only the pale sands of the overburden are 
here visible. 
HERNANDO COUNTY. 
Phosphate is being produced in Hernando County in the vic¬ 
inity of Croom. The mine in operation here is a dredge mine. 
The relation of the phosphate formation to the underlying lime¬ 
stone as seen in an abandoned pit several miles west of Croom is 
the same as that in other parts of the phosphate section, the lime¬ 
stone projecting as rounded peaks. The material above the phos¬ 
phate stratum consists largely of incoherent sands. The usual 
gray phosphatic sands weathering purple on exposure are seen sur¬ 
rounding the phosphate rock. In the mines near Croom a con¬ 
siderable amount of clay is associated with the phosphate. 
