MINERAL INDUSTRIES FULLERS EARTH. 33 



e 



plished by blowing dry steam through the refined oil which is 

 heated to a temperature above the boiling point of water. A 

 serious difficulty in the use of this clay is the rapid oxidizing action 

 which some fullers earths have on edible oils. In milling practice 

 air is blown through the filter press to force out the oil remaining 

 in the earth after treatment. With some of the earths the oxidiz- 

 ing action is so rapid that the oil remaining in the earth takes 

 fire, or is liable to take fire at this time. It is to be hoped that 

 this difficulty will be overcome. 



DISTRIBUTION OF FULLERS EARTH IN THE UNITED STATES. 



Clays having the properties of fullers earth more or less well 

 developed are widely distributed in the United States and are con- 

 fined to no particular geological horizon, although the largest 

 known deposits are of Cenozoic age. By far the greater part of 

 fullers earth is in the form of a sedimentary deposit which is dis- 

 tinctly stratified, and from which an overburden must be removed 

 in mining. In Arkansas, however, fullers earth is known that is 

 exceptional in that it is residual, having been formed in situ from 

 the disintegration of basaltic dykes.* In the United States fullers 

 earth is known from the following states : Alabama. Arizona, 

 California, Colorado, Florida, Georgia, Massachusetts, Minnesota, 

 Mississippi, New York, South Carolina, South Dakota, Texas and 

 Utah. Of these states, 'however, only six were actively producing 

 fullers earth during 1913, as follows: Florida, Georgia, Arkan- 

 sas, California, Colorado and Massachusetts. 



The fullers earth of southern Georgia, which is worked at 

 Attapulgus near the Florida line, represents a northward extension 

 of the Florida deposits. In central Georgia near Macon, however, 

 is found a dififerent type of earth, which according to the Georgia 

 Geological Survey is found in the Claiborne formation of Eocene 

 age. This earth differs in some important respect"^ from that of 

 Florida, being used chiefly for vegetable oils, while that from 

 Florida finds its chief use at present in clarifying mineral oils. 

 The fullers earth of Arkansas is used chiefly in clarifying vegetable 

 oils. The fullers earth of Colorado is said to be used in bleach- 



*Residual fullers earth is said to occur also in Saxony where it is found 

 m situ derived from ^abbro. 



