MINERAL INDUSTRIES. 
35 
find their greatest usefulness in country sections where cheapness 
in road-making is necessary. 
The road-making clays are of a red or yellowish color, indicat¬ 
ing a high percentage of iron compounds which probably assist in 
the bonding power of the material. In texture the clay is rather 
coarse and breaks up readily. 
BOG IRON ORE. 
Bog iron ore occurs in various parts of the State, but is usually 
in thin deposits and of local extent. It has been stated by Shaler 
(U. S. Geological Survey, 15th Ann. Rept., p. 272, 1895), that 
where the surface of a limestone road can be covered with iron ore 
the firmness of the mass is much increased. An iron oxide, such as 
bog iron ore, serves as a cementing material, and this is doubtless 
the explanation of its usefulness for this purpose. 
Low grade phosphate may serve in some localities as a useful 
road rock. The hard rock phosphate is harder than limestone and 
is reported to have better cementing qualities. Phosphate screen¬ 
ings have been used to some extent and have proved satisfactory. 
SAND-LIME BRICK. 
Four companies were actively engaged in the manufacture of 
sand-lime brick in Florida during 1915 as follows: The Bond 
Sandstone Brick Company, Lake Helen, Fla.; The Composite Brick 
Company, 425 St. James Bldg., Jacksonville, Fla.; The Plant City 
Composite Brick Company, Plant City, Fla., and The Valrico Sand¬ 
stone Company, Valrico, Fla. 
The total production of sand-lime brick in Florida during 1915 
including common, front and fancy brick, was valued at $77,575- 
SAND AND GRAVEL. 
The sand produced in Florida is used for building and paving 
and for railroad ballast. The gravel produced finds its chief use 
for road making and for road ballast. The total production of 
sand and gravel for 1915 was 123,548 tons, valued at $34,055. 
The companies reporting the production of sand and gravel in 
Florida during 1915 are the following: 
Atlantic Coast Line Railroad Company. 
Florida Sand and Shell Company, Tampa. 
Interlachen Gravel Company, Interlachen. 
