248 
FLORIDA state; geological survey. 
Flint is chemically an oxide of silica SiCh with more or less ac¬ 
companying impurities. It is a variety of the mineral quartz, occur¬ 
ring massive and non-crystallized or more accurately very imperfectly 
crystallized (cryptocrystalline). The term chert is often used inter¬ 
changeably with flint. Properly chert is an impure flint or flinty rock. 
Flint and chert are lacking in cleavage. They break, as do the other 
varieties of quartz, with conchoidal fracture. A flint rock when 
crushed breaks into sharp cornered pieces of varying size. 
Properties:—The mineral quartz, of which flint is a variety, has a 
hardness of seven on a scale in which the hardest mineral diamond, is 
ten. The varieties of quartz vary in hardness slightly according to 
the impurities that they contain. Silica is one of the least soluble of 
minerals and among the' most resistant to decay. 
Occurrence of Flint and Chert in Florida:—Flint and chert occur 
mostly as masses or “horsebacks” in the limestone formations. A 
good illustration of the manner of occurrence may be seen in phos¬ 
phate pits or in some of the pits of the Florida Lime Co., at Ocala. 
In some of the sinks on Thompson’s farm two miles east of Sumter- 
ville will be seen flint masses exposed by the natural decay of the 
limestone. The flint masses appear to conform to no rule as to size 
and extent. They may form ridges running through the limestone; 
or again they may occur as rounded or elongate masses. Occasionally 
the flint forms as a thin stratum lying horizontally. This flint bearing 
limestone lies at no great distance from the surface throughout all of 
the central peninsular section of the State from Columbia County on 
the north to Sumter County on the south and from the Suwanee 
River and the Gulf coast to east Alachua and Marion Counties. Much 
of the hard rock phosphate rests upon and in this flint-bearing lime¬ 
stone, and from the phosphate pits great quantities of the flint may 
be obtained. Occasional flint hills such as that crossed near Evinston 
and Micanopy stand out as evidence of the resistance of flint to the 
weathering agencies, the surrounding limestone having disappeared 
through erosion. This flint lies chiefly within the Vicksburg lime¬ 
stones (see map). It is not to be inferred, however, that no other 
Florida formations contain silica. On the contrary, many of the 
formations are highly siliceous. The Vicksburg limestones are, how¬ 
ever, the chief flint-bearing formations of Florida. 
Origin of the Flint in the Vicksburg Limestones:—The flint occurs 
as has been stated, in masses irregularly distributed through the lime¬ 
stone. Well drillers can bear witness to the frequency of flints and 
to their distribution through the limestone to a great depth. The flint 
masses were clearly not present in the limestone as originally formed. 
