ANNUAL REPORT-MINERAL INDUSTRIES. 
41 
the other limes are used when slow-setting limes are 
desired. After calcination, the lime may he placed on the 
market as quick lime, or it may be slaked and placed on 
the market as hydrated lime. Hydrated lime is said to 
be desirable for certain purposes since the lime if properly 
slaked breaks up into exceedingly fine powder. 
The Florida Lime Co., of Ocala, operated three lime 
plants during 1907. The limestone used is from the for¬ 
mation known as the Ocala Limestone, which is well ex¬ 
posed in and about Ocala. This formation is, however, 
not restricted to Marion County, but extends as the sur¬ 
face formation south to Sumter County and northwest to 
Columbia County. 
Natural Cement. 
Practically all limestones contain some sandy and 
clayey impurities. When the amount of clay material 
present exceeds a certain percentage the product result¬ 
ing upon burning will set under water and is known as 
a natural hydraulic cement. Bleininger classes the nat¬ 
ural cements as (1) hydraulic limes and (2) Roman 
cements. The hydraulic limes in this classification are 
those which contain from 75 to 80 per cent of calcium 
carbonate and from 20 to 25 per cent of clay. The Roman 
cements contain 50 to 75 per cent, of calcium carbonate 
and 50 to 30 per cent, of clay. Peppel, however, proposes 
to place the range of sandy and clayey matter in hydraulic 
limes at 5 to 10 per cent, while the range in the natural 
or Roman cement is given as 10 to 30 per cent. The 
practical distinction between the hydraulic limes and 
Roman cements is that the former after burning and upon 
exposure to the air slake by themselves and evolve consid¬ 
erable heat, while the latter burn to a cinder which must 
be ground; they also evolve less heat of hydration on 
slaking than do the limes. 
No cements other than lime are at present being manu¬ 
factured in Florida. Hydraulic cement was formerly 
