300 Sehaller — Chemical Composition of MoVybdic Ocher. 



For the material from the other localities,* the quantity was 

 so small that exact values cannot be expected, but the analyses 

 all show a general agreement with the calculated values. The 

 samples analyzed are as follows : 



No. 1 is from Telluride, Colorado, and is from the sample 

 furnished by the Foote Mineraf Company, of Philadelphia. 



No. 2 was very kindly furnished by Prof. A. J. Moses, of 

 Columbia University, who states that the sample is probably 

 from California, though the locality is not known for certain. 

 Two samples were sent, one yellow, which was seen to be pure, 

 and one brown, which was seen under the microscope to consist 

 of a mixture of the pure yellow mineral and limonite. This 

 sample at once suggested that it was similar to that analyzed 

 by Owen, who obtained 35 per cent Fe„0 3 . It also showed the 

 ease with which a mechanical mixture of molybdite and limonite 

 could be detected under the microscope. The opaque brown 

 limonite was scattered through some of the yellow molybdite, 

 and caused it to appear almost opaque, besides which there 

 were numerous patches of earthy limonite. The brown sam- 

 ple was not analyzed. 



No. 3 is from Renfrew, Ontario, and was very kindly fur- 

 nished by Prof. C. Palache, of Harvard University. Most of 

 the material is massive and earthy appearing, though seen under 

 the microscope to consist of minute librous crystals. The 

 material did not look promising, but analysis showed values 

 agreeing well with the other. Owing to an accident, only the 

 iron and molybdenum could be determined. These values are 

 not given. On one of the specimens sent by Prof. Palache, 

 there was a small amount of the finely crystallized fibrous ma- 

 terial which seemed to be very pure. This was scraped off and 

 analyzed, and though only about fifty milligrams were available, 

 the results given under No. 3 were obtained. 



The methods of analyses were like those mentioned with the 

 analyses of the New Hampshire material. By heating in a 

 closed tube, to obtain the water, some of the molybdenite which 

 was usually mixed with the mineral doubtless oxidized to the 

 oxide, thus increasing the amount of molybdenum present.. 

 The results obtained are : 



H„0---- 



Fe„O s 



Mo0 3 



Insol - 



100-0 102-9 97-9 



* The characteristic optical properties of the ferric rnolybdate were also 

 determined on specimens from Stanhope, New Jersey ; Gold Creek, Deer 

 Lodge Co. , Montana ; Aldfield Township, Pontiac Co , Quebec. 



No. 1 



No. 2 



No. 3 



Colorado 



California 



Ontario 



15-8 



15-4 



15-5 



19-0 



15-8 



17-3 



59-3 



47-7 



55-7 



[5-9] 



24-0 



9-4 



