THE NONMETALLIC MINERALS. 



347 



result is a very strong 1 mortar, in some cases stronger than when sand 

 is employed. 1 



The so-called gumbo clays, sticky, tough, and dark-colored clays 

 of the Chariton River region, Missouri, are hard burned and used for 

 railroad ballast and macadam. 



Under the names of -Rock Soap and Mineral Soap there have from 

 time to time been described varieties of clay which, owing to their 

 soapy feeling, are suggestive of soap, and which in a few instances 

 have been actually used in the preparation of this material. 



A rock soap from Ventura County, California, has been described 

 by Prof. G. H. Koenig as a mixture of sandy and clayey or soapy 

 material in the proportion of 45 per cent of the first and 55 per cent 

 of the second. The chemical composition of the material and of the 

 two portions is given below: 



Nearly all the silica is reported as being in a soluble or opalescent 

 state and the alumina as either a hydrate or very basic silicate. It is 

 said 2 that at one time the material was made into a variety of use- 

 ful articles, as "salt water soap," scrubbing and toilet soap, tooth pow- 

 der, etc. 



A somewhat similar material from Elk County, Nevada, has been 

 used for like purposes, and put upon the market under the name of 

 San-too-gah-choi mineral soap. This clay is of a drab color, with a 

 slight pinkish tint, a pronounced soapy feeling and slight alkaline 

 reaction when moistened and placed upon test paper. An analysis by 

 Packard in the laboratory of the U. S. National Museum yielded: 



Silica 48.80 



Alumina 18.57 



Iron oxides 3. 88 



Lime 1. 07 



Magnesia 2. 52 



Soda 2.32 



Potash 1.12 



Ignition 21.13 



Total. 



1 The Worlds Progress, February, 1893. 



2 Sixth Annual Report of the State Mineralogist of California, 1886, Pt. 1, p. 132. 



