36 The American Geologist. juiy, 1901. 
no decided appreciable difference in the coin])osition of the two 
parts of the mineraL 
In its purest form bauxite contains more or less foreign 
material either chemically combined or mechanically admixed. 
Iron oxide present in variable amounts, ranging from a trace to 
percentages equal to and occasionally exceeding that of the 
alumina, is usually present replacing in part the alumina, and 
in part only as an impurity. 
Titanium is invariably present ranging usually from i to 10 
per cent, when estimated in the form of titanium dioxide. 
Anah'ses indicate that this constituent averages higher in the 
pisolitic ore and is lowest in the structureless bauxitic clays. 
The form in which the titanium exists in the ore is seemingly 
dependent in large measure upon the origin of the bauxite. A 
study of those deposits derived from basalt and similar igneous 
rocks indicates that the titanium occurs in the form of free ox- 
ide or as titanic iron. This is true of the Vogelsberg deposits 
in' Germany as shown in the study of thin sections of the bauxite 
by A. Liebreich ; and also^ of the Ober-Hessen deposits by Lang. 
Very little if any of the titanium in the Georgia deposits exists 
in the form of free oxide, as a microscopic examination of a 
large number of thin sections of the mineral failed to indicate 
more than a bare trace of titaniferous oxides. Separation by 
means of heavy solution and by elutriation confirmed the micro- 
scopic evidence. 
Silica varies from a fraction of i per cent to several per 
cent, in the purest ore, and 30 to 35 per cent, in the low grade 
tvpes of material, bauxitic clays and kaolins. This constitvtent 
is usually present in the form of the hydrated aluminum silicate 
clay, which is invariably admixed in varying proportions with 
the bauxite ; and is also present to some extent as free silica, as 
shown by the microscope. 
The Georgia bauxites are usually free from traces of the 
additional following common impurities in bauxites of many 
localities : lime, magnesia, phosphoric and carbonic acids and 
the alkalies, soda and potash. 
R£SUM£ : From the preceding data it is clear that the 
formula given by Laur for the French bauxites essentially the 
bihydrate of alumina and applied to the Georgia-Alabama min- 
eral is not applicable to the Georgia deposits. The average 
