60 Chemical Examination of American Minerals. 



2 atoms sesquisilicate of lime, - - 13 



1 atom silicate of iron, _ _ - G-5 



1 atom silicate of manganese, - - 6-5 



20-00 



From the analyses and calculations of Count Trolle Wacht- 

 meister,* it follows that the garnet varies a good deal in its 

 composition. It is usually a compound of two different sili- 

 cates, which may be any two of the following. 



Silicate of lime. 

 Silicate of alumina, 

 Silicate of iron. 

 Silicate of manganese. 

 Silicate of magnesia. 



The variety just described, contains an atom more silica 

 than usually exists in garnet. It contains three bases, and no 

 variety of garnet hitherto analyzed, has been found to contain 

 so much manganese. 



22. PIPE-STONE. 



I give this name to a curious stone from North America, 

 which the Indians make use of for constructing tobacco-pipes. 

 For the specimen which I analyzed, I am indebted to Dr. 

 Scouler, who, some years ago, went out as a surgeon in one 

 of the vessels sent to the west coast of North America by the 

 North-west Company. He spent a summer between Nootka 

 Sound and the Columbia river. Among other natural pro- 

 ductions of the country, he brought home a specimen of this 

 pipe-stone. He got it from the Indians, and was not posses- 

 sed of any information respecting the part of the country, or 

 the nature of the rocks where it is found. 



* Kongl. Vetensk. Acad. Handl. 1823. p. 120. 



