GEOLOGY BETWEEN APALACHICOLA AND OCKLOCKNEE RIVERS. 19 
An account of the fullers earth deposits of Gadsden county 
was given in the. Second Annual Report of this Survey in 1909. 
This is now out of print and the following has been adapted from 
this report, with some omissions, and additions where necessary, 
in order to bring the matter relative to the deposits up to date. 
Fullers earth is a clay differing from other clays chiefly in that 
it is light and porous, and possesses in a high degree the quality of 
absorbing greasy substances. This earth was formerly used in 
removing grease and fats from cloth in the process of fulling, 
from which usage it received the name of fullers earth. But little 
earth is used for this purpose at the present time, soaps and alka- 
lies having almost entirely replaced it. 
Fullers earth, like other clays, is complex. It consists not of a 
single mineral, but of a variety of minerals; the mineral particles 
being mixed in widely varying proportions, resulting in a variable 
chemical and mineralogical composition. Under the microscope 
the Gadsden county fullers earth shows angular particles of quartz 
together with green double refracting particles which Merrill re- 
gards as a siliceous mineral.* In fullers earth from Arkansas, 
Merrill observed sharply angular colorless mineral particles, faintly 
double refracting, but lacking crystal outlines or other physical 
properties such as would determine their exact mineral nature. 
Angular particles of quartz and a few yellowish iron-stained 
particles suggestive, of residual products from decomposition 
of iron magnesia silicates were also recognized in this sample. 
The fullers earth from Surrey, England, according to the same 
writer, consists of extremely irregular eroded particles of a sili- 
ceous mineral and of minute colorless particles suggestive of a 
soda lime feldspar. Thus it may be said that while fullers earth 
is known to consist like most other clays of a mixture of minerals 
it is often difficult to make a satisfactory determination of the 
individual mineral constituents. 
Chemical Constituents : — There is a wide range in variation in 
the chemical constituents of different fullers earths, or fullers earth 
from different localities. The range of individual constituents 
may be inferred from the accompanying analyses. 
* Report of the U. S. Nat. Museum, 1899, p. 338. 
