SOME CRYSTAL MEASUREMENTS OP CHILLAGITE. 207 



SOME CRYSTAL MEASUREMENTS OP CHILLAGITE, 



By Miss C. D. Smith, b.Sc, and Leo A. Cotton, b.a., b.Sc, 



Department of Geology, University of Sydney. 



[With Plates XV, XVI.] 



[Read before the Royal Society of N. S. Wales, December 4, 1912.'] 



The crystals measured and discussed in this paper were 

 kindly supplied to us by Mr. A. J. Ullmann of Chillagoe. 

 In December of last year Mr. Ullmann wrote to Professor 

 David, reporting to him the discovery of what he thought 

 was a new mineral, and forwarding a sample of the same. 

 The new substance was stated by Mr. Ullmann to contain 

 lead, molybdenum and tungsten. It is thus related to both 

 stolzite and wulfenite. As no such mineral combination 

 had hitherto been recorded, the name Chillagite was 

 suggested by Professor David. 



The Queensland Department of Mines also obtained 

 samples of the material from the same mine, and an 

 analysis was prepared which was published in February of 

 of the present year. This analysis corresponds closely to 

 the formula PbO Mo0 3 PbO W0 3 . Shortly after this Mr. 

 Ullmann submitted a note to this Society giving an account 

 of the occurrence of the mineral and also the results of a 

 qualitative analysis. He also stated that the composition 

 was PbO Mo0 3 PbO W0 3 and gave the theoretical pro- 

 portions of PbO, M0O3 and W0 3 for this formula. 



In June last, the Queensland Department of Mines for- 

 warded Professor David a copy of a report embodying still 

 later analyses. That portion of the report giving the 

 analyses reads as follows : — 



"The report on the previous sample was made on a limited 

 supply of crystals, but the present sample was sufficiently large to 

 allow a more general examination to be made. The present 

 sample differed from the previous one in containing a considerable 



