127 



On a Ne^w' Mineral (Stibiotantalite). 



By G. A. GoYDER, F.C.S., Assayer, School of Mines. 



[Read April 4, 1893.] 



Some samples of this mineral were given to Mr. J. J. East, 

 Registrar of the School of Mines and Industries, Ijy Mr. Knox 

 Brown, of Bunbury, West Australia, the latter explaining that 

 although the sluiced tin-ore from the alluvial at Greenbushes 

 appeared to the miners of a fair, even character as regards 

 freedom from associated minerals, the assay values from Mel- 

 bourne varied in a most irregular manner. Mr. East's attention 

 was taken with part of the sample submitted, which had been 

 called locally " pale tin " and " resin tin." On being submitted 

 to a preliminary examination m the School Laboratory this was 

 found to contain antimony, but did not appear to have the pro- 

 perties of any of the ordinary antimonial minerals. 



Mr. East then handed it to me for analysis, the result of which 

 was as fallows : — 



Tantalic acid, Ta^O^ ... ... 51-13 per cent. 



Niobic acid, Nb^O. 7-56 " 



Antimony oxide, SbgO 3 ... 40'23 " 



Bismuth oxide, Bi^O 3 0-82 " 



Mckel oxide, NiO 0-08 



99-82 

 From the above analysis it appears that the mineral consists 

 essentially of tantalate of antimony, part of the tantalic acid 

 being replaced by niobic acid, and part of the antimony by 

 bismuth. 



No record could be found in any of the text-books of miner- 

 alogy of any mineral constituted as above, and in none of the 

 published analyses of the tantalates is there a trace of antimony 

 reported. 



Physical Properties, &c. 



The specific gravity of different samples of the mineral was 

 found to vary from 6-47 to 7-37, the latter being the S.G. of the 

 sample analysed. All the specimens were waterworn, and 

 although some of them, if not all, were crystalline, the form 

 could not be determined. Fracture uneven to sub-conchoidal 



