A PRELIMINARY REPORT ON CLAYS OF FLORIDA 69


 CHAPTER II


 CLASSIFICATION OF CLAYS

 Clays may be classified in a variety of ways, according to their origin, mode of occurrence, properties, or uses. No classification yet proposed, however, has satisfactorily treated such a diversity of factors. A classification based upon thae origin would l:e of special interest to the geologist, while a ceramist would Le more keenly interested in one based upon their physical properties. A classification based upon the uses of clays is probably the least satisfactory of any due to the fact that there is a very great range in the kind of clay used for any one purpose, and that one clay may be used for several different purposes.
 In the past three decades no less than nine1 separate classifications have appeared in the literature dealing with clays. While none of these are satisfactory in every respect, three of them deserve careful consideration.
 Ries's2 classification is based primarily on the geological occurrence and secondarily on the firing qualities of clays. It follows:

 A. Residual clays. (By decomposition of rocks in situ.)
 I. Kaolins or china clays. White-burning.
 (a) Veins, derived from pegmatite.
 (b) Blankets, deposits, derived from extensive areas of igneous or metamorphic rocks.
 (c) Pockets in limestones, as indianaite.
 II. Red-burning residuals, derived from different kinds of rock.
 B. Colluvial clays, representing deposits formed by wash from the foregoing and of either refractory or non-refractory character.

 'Orton, E., Clays of Ohio, Ohio Geol. Survey, VII, p. 52, 1893.
 Wheeler, H. A., Clay Deposits, Missouri Geol. Survey, XI, p. 25, 1896.
 Ladd, G. E., Preliminary Report on the Clays of Georgia, Georgia Geol. Survey, Bull. 6A, p. 12, 1898.
 Buckley, E. R., The Clays and Clay Industries of Wisconsin,'Wis. Geol. Survey Bull. 7, Part I, p. 14, 1901.
 Orton, E., Jr., Quoted by Beyer, S. W., and Williams, I. A., Technology of Clays, Iowa Geol. Survey, Vol. XIV, p. 40, 1903.
 Grimsley, G. P., Clays, Limestones, and Cements, West Va. Geol. Survey, Vol. III, p. 70, 1905.
 Ries, H., Clays, Their Occurrence, Properties and Uses, p. 27, 1908.
 Grout, Frank F., and Soper, E. K., Preliminary Report on the Clays and Shales of Minnesota, Minn. Geol. Survey, Bull. II, p. 18, 1914.
 Parmelee, C. W., Further Investigation of Illinois Fire Clays, Bull. 38, 11. Geol. Survey, p. 10, 1921.
 2Ries, H., Clays, Their Occurrence, Properties and Uses, p. 27, 1908.