u 
FLORIDA GEOLOGICAL SURVEY. 
several minerals making up a clay. This is true of 
fuller’s earth as of other clays. Under the microscope 
the Gadsden County fuller’s earth shows angular parti¬ 
cles of quartz together with green double refracting par¬ 
ticles which Merrill regards as a siliceous mineral.* In 
fuller’s earth from Arkansas, Merrill observed sharply 
angular colorless mineral particles, faintly double refract¬ 
ing, but lacking crystal outlines or other physical prop¬ 
erties 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 recog¬ 
nized in this sample. The fuller’s earth from Surrey, 
England, according to the same writer, consists of ex¬ 
tremely irregular eroded particles of a siliceous mineral 
and of minute colorless particles suggestive of a soda lime 
feldspar. Thus it may be said that while fuller’s earth is 
known to consist like most other clays of a mixture of 
minerals, a satisfactory determination of these minerals 
hais not yet been made. 
, Chemical Constituents:—There is a wide range in vari¬ 
ation in the chemical constituents of different fuller’s 
earths, or fuller’s earth from different localities. The 
range of individual constituents may be inferred from 
the accompanying analyses. 
ANALYSES OF FULLER’S EARTH FROM VARIOUS LOCALITIES. 
I. 
II. 
III. 
IV. 
V. 
VI. 
Silica (Si0 2 ). 
G2.83 
67.46 
58.72 
50.36 
74.90 
63.19 
Alumina (AUG.,) .... 
.10.35 
10.08 
16.90 
33.38 
10.25 
18.76 
Ferric Oxide (Fe 2 0 3 ) 
. 2.45 
2.49 
4.00 
3.31 
1.75 
7.05 
Lime (CaO). 
. 2.43 
3.14 
4.06 
1.30 
0.78 
Magnesia (MgO)- 
. 3.12 
4.09 
2.56 
2.30 
1.68 
Potash (K^O). 
Soda (Na 2 0). 
.0.74 
. 0.20 
2.11 
1.75 
0.21 
1.50 
Water (H 2 0). 
. 7.72 
5.61 
8.10 
12.05 
5.80 
7.57 
Moisture . 
..6.41 
6.28 
2.30 
1.70 
Loss on ignition. 
11.86 
.... 
* Report of the U. S. National Museum 1899, p. 338. 
