286' Lindgren and Melville — Socialite- Syenite 



Analyses Nos. I and II give the ratio of 1 : 1 for the atomic 

 ratio of these metals to the oxygen, and Nos. Ill and IV give 

 approximately the same, from which it appears that we have a 

 mixture of colnmbous and tungstons oxide in these residues 

 and that the triangular prisms are crystals of the latter. 



Tungstons oxide — WO — as thus obtained crystallizes in the 

 hexagonal system, mostly in hemi prisms having a light gray 

 to tin white color, a metallic luster, a hardness greater than 

 glass, and a dark gray streak. Hydric chloride, fluoride, and 

 sulphate, also a boiling solution of potassic hydrate have no 

 perceptible action on it, but hydric nitrate and aqua regia 

 attack it, especially when heated, converting it slowly into 

 tungstic acid. The crystals can be kept under water or 

 exposed to the air at ordinary temperatures without change, 

 but when heated to redness in the air they are gradually con- 

 verted into tungstic acid ; this change takes place without 

 incandescence but is accompanied by a considerable increase 

 in volume, less, however, than that which accompanies the 

 corresponding conversion of columbous oxide into columbic 

 acid which is accompanied by incandescence. 



The tungstous oxide was probably formed in this case by 

 the action of stannous oxide, formed in the repeated liqua- 

 tions of the tin, upon metallic tungsten which had been re- 

 duced in the original tin charge. 



State School of Mines, Rapid City, S. D. 



Art. XXXIV. — A Socialite-Syenite and other Rocks from 



Montana ; by Waldemar Lindgren, with Analyses by 

 W. H. Melville. 



Among the collections in the U. S. National Museum there 

 is a suite of specimens, principally of eruptive rocks, collected 

 in the northern part of Montana, by Dr. C. A. White and 

 Mr. J. B. Marcou during the summer of 1883. The principal 

 localities where the collections were made are the Moccasin 

 Mountains, the Bear Paw Mountains, and Square Butte, near 

 the Highwood Mountains. Rocks from these places have not 

 been previously examined, as far as I know, and it is only pro- 

 posed in this paper to describe in detail one which appears of 

 particular interest ; the general character of the collection, 

 however, may be briefly noted. All of the igneous rocks 

 collected appear to belong to the class of post-Cretaceous intru- 

 sive rocks which has such a wide distribution in the Rocky 

 Mountains and which range from the most acid to the most 



