418 



schaller: ilsemannite 



Furthermore, the mineral is a sulphate and is not an oxide nor a 

 molybdate of molybdenum. 



The occurrence of ilsemannite near Ouray, Utah, has been 

 investigated from the geological side by Frank L. Hess of the 

 United States Geological Survey, who is preparing a report on 

 this subject. The present paper, which is of a preliminary 

 nature, aims to give briefly the mineralogical features of the 

 blue molybdenum mineral, as the complete study has been un- 

 avoidably interrupted for a time. 



The ilsemannite from Ouray, Utah, is disseminated through 

 a rock, analysis of which shows that about 10 per cent of the 

 sample is soluble in cold water. The analytical figures are 

 given in Table 1. 



TABLE 1 



Analysis of Rock Containing Disseminated Ilsemannite, from near Ouray, 



Utah 



The water-soluble portion contains iron sulphate, and the 

 consumption of permanganate in titrating this solution exactly 

 equals the amount of iron (as ferrous iron) determined gravi- 

 metrically. There is present, therefore, only an undeterminable 

 amount of molybdenum in a lower state of oxidation. Wells 2 

 found similarly that the deep-blue mine water from the Lucania 

 tunnel, Idaho Springs, Colo., although containing 7.98 grams 

 M0O3 per liter, contained only an undeterminable trace of Mo0 2 . 

 The coloring effect of this trace of Mo0 2 seems to be very intense. 



2 Quoted by Horton, F. W., in Molybdenum: its ores and their concentration. 

 U. S. Bur. Mines Bull. Ill, p. 15. 1916. 



