406 W. T. Schaller — Supposed Vanadic Acid. 



The color of much of the Lake Superior material is yellow 

 suggesting that the substance is more likely a cuprous hydroxide 

 rather than the simple oxide. The minute size of the crystals, 

 however, also tends to change the red color of cuprite to a 

 yellow. A similar tendency was noted for the red oxide of 

 mercury, montroydite, which, in the larger crystals* is a deep 

 red, but in feltlike masses composed of minute prismatic crys- 

 tals is a light yellow brown and as spherical masses composed 

 of minute bristling prismatic crystals is almost light yellow in 

 color. 



A microscopic examination of chalcotrichite crystals from 

 Arizona showed moreover that whereas most of the crystals 

 were a deep brownish red, the thinner ones were yellowish 

 brown and the very thinnest ones were yellow. These yellow 

 crystals were much thicker than any of those from the Lake 

 Superior specimen. It may well be, therefore, that both the 

 Lake Superior specimen and the hydrocuprite from Pennsyl- 

 vania are, in fact, only cuprite and not a distinct cuprous 

 hydroxide. 



A second occurrence of " vanadium ocher " was mentioned 

 by Goyderf in his description of sulvanite. A specimen of 

 sulvanite in the collection of Colonel Roebling contained a 

 considerable amount of this " vanadium ocher " which was 

 readily identified as cuprodescloizite. In 1909, K. A. Nenad- 

 kevichj very briefly described a new mineral from the province 

 of Ferghana in Russian Turkestan. This mineral is dark red, 

 silky, soft and moss-like, and was named alaite. Its composi- 

 tion was stated to be V 2 5 .H 2 0, but no analysis was given. 

 Alaite may prove however to be a calcium vanadate either 

 related to or identical with hewettite. 



The important result obtained is that the so-called vanadic 

 ocher from Lake Superior is free from vanadium and is to be 

 stricken from lists of vanadium minerals. 



* Hillebrand, W. F., and Schaller, W. T. : The mercury minerals from 

 Terlihgua, Texas, Bull. 405, U. S. Geol. Survey, 1909. 



+ Goyder, G. A. : Sulvanite, a new mineral, Jour. Chem. Soc, London, 

 vol. lxxvii, p. 1094, 1900. 



X Bull. Acad. Sci., St. Petersburg, p. 185, 1909. 



