A PRELIMINARY RE PORT ON CLAYS OF 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 13100 C. (cone 9)1, although in the presence of alkalies this temperature is much lower. ClarkeC4 gives the melting point of feldspar as ranging from 12650 to 15500 C. He points out, however, that these observations were made upon artificial preparations of great purity.
 COMPOSITION OF- VrLDSPARS'
 Chemical Composition
 Feldspar Speciesi
 ______________ 2__ I Al-003 I K20 Na20 Ca0
Orthoclase ......................64.70 18.40 16.90 0.00 I 0.00
Albite ..........................68.00 20.00 00.00 12.00
Oligoclase ......................62.00 24.00 00.00 9.00 5.00
Labradorite .....................53.00 30.00 00.00 4.00 I13.00
Anorthite .......................43.00 37.00 00.00 0.00 I20.00

 11ica-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 temperature. 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 mnica is muscovite because it is less easily weathered.
 Hydromzica-Hydromica is, according to Somers2 a distinctly micaceous 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 himr. Hydromica is peculiarly abundant in many clays.

 3Ries, H., Clays, Their Occurrence, Properties and Uses, p. 55, 1908.
 4Clarke, F. W., Data of Geochemnistry, U. S. Geol. Survey Bull. 695, p. 360, 1920.
 1Ries, H., Clays, Their Occurrence, Properties and Uses, p. 55, 1908.
 2Somers, R. E., Microscopic Study of Clays, in U. S. Geol. Survey, Bull. 708, p. 296, 1922.