A PRELIMINARY REPORT ON CLAYS OE FLORIDA 
73 
Feldspar —This mineral as a rule is' not abundant in clays, though 
it decomposes more readily than quartz and thus usually occurs in 
smaller grains. Feldspar occurs in several forms which differ slightly 
in their chemical compositions. While these different species of feldspar 
vary to some extent in their melting points it may be said that feldspar 
fuses at about 1310° C. (cone 9) 3 , although in the presence of alkalies 
this temperature is much lower. Clarke 4 gives the melting point of feld¬ 
spar as ranging from 1265° to 1550° C. He points out, however, that 
these observations were made upon artificial preparations of great 
purity. 
COMPOSITION OF FELDSPARS 1 
Feldspar Species 
Chemical Composition 
Si 02 
AI 2 O 3 
k 2 o 
1 
Na 2 0 
CaO 
Orthoclase . 
64.70 
18.40 
16.90 
0.00 
0.00 
Albite . 
68.00 
20.00 
00.00 
12.00 
12.00 
Oligoclase .. 
62.00 
24.00 
00.00 
9.00 
5.00 
Labradorite . 
53.00 
30.00 
00.00 
4.00 
13.00 
Anorthite .. 
43.00 
37.00 
00.00 
0.00 
20.00 
Mica —This is another mineral which occurs in the form of several 
different species which likewise have a variation in their different 
compositions. Mica occurs in most clays and is very difficult to 
remove. In washing, on account of its light scaly character, it floats off 
with the clay particles. Mica acts as a flux in clays at a high tempera¬ 
ture. It is abundant in the clays of Florida. Few clays of the State are 
free from it, while in some of those in the western counties it is present 
in large quantities. The chief mica is muscovite because it is less easily 
weathered. 
Hydromica —Hydromica is, according to Somers * 1 2 a distinctly mica¬ 
ceous mineral which represents a transition stage of weathering between 
sericite and kaolinite, with kaolinite as the final product. Somers reports 
hydromica as scarce in only twenty-two and unidentifiable in twelve of 
the clays examined by him. Hydromica is peculiarly abundant in many 
clays. 
3 Ries, H., Clays, Their Occurrence, Properties and Uses, p. 55, 1908. 
4 Clarke, F. W., Data of Geochemistry, U. S. Geol. Survey Bull. 695, p. 360, 1920. 
1 Ries, H., Clays, Their Occurrence, Properties and Uses, p. 55, 1908. 
2 Somers, R. E., Microscopic Study of Clays, in U. S. Geol. Survey, Bull. 708, 
p. 296, 1922. 
