4:42 PROCEEDINGS OF SECTION C. 



12.— TANTALUM AND NIOBIUM IN AUSTRALIA. 



By EDWARD 8. SI UPSON, B.E., F.C.S., of tJie Geological Survey of Western 



Australia. 



In the census of minerals of Australia submitted to the Association 

 in 1890 no mention is made of any mineral containing tantalum and 

 niobium. Since then, however, these rare metals have been recognised 

 in several widely separated districts in the Commonwealth, and, in 

 response to the recent commercial demand for tantalum ores, deposits 

 of great richness and extent have been disclosed in the Pilbara Gold- 

 field of Western Australia. In this paper an account will be given of 

 the discovery of these interesting minerals in Australia, their mode of 

 occurrence, and their chemical and physical characteristics. 



GENERAL FEATURES OF OCCURRENCE. 



Before dealing with purely Austrahan deposits, it will be well to 

 go briefly into the general features of the question. 



These two metals are nowhere found in the native state, nor in 

 sulphide or other similar minerals, but exist always in combination 

 with oxygen and one or more other -metals, the oxides having an acid 

 character and giving rise to tantalates and niobates. They invariably 

 occur in conjunction, replacing one another isomorphously to a very 

 variable extent, the niobate of a metal often passing by insensible 

 gradations into the tantalate without change of form or physical 

 characters other than a corresponding gradual rise in specific gravity, 

 tantalum having an atomic weight double that of niobium. In the 

 following pages, therefore, whenever a mineral is described as a tanta- 

 late it must be understood that it contains niobium as well as tantalum, 

 but that the former is present in preponderating amount, and vice versa. 



The ores hitherto detected in Australia are : — 



(1) Columbite, niobate of iron and manganese. 



(2) Tantalite, tantalate of iron and manganese. The sub- 



species manganotantalite contains more manganese than 

 iron ; the normal variety more iron than manganese. 



(3) Stibiotantalite, tantalate of antimony. 



(4) Microlite, tantalate of lime. 



(5) Euxenite, titanoniobate of yttrium, erbium, cerium, &c. 

 Until recently the best-known localities of the mineral tantalates 



and niobates were Sweden, Norway, Bavaria, Siberia, Greenland, and 

 the United States. Though occasionally recorded as occurring in 

 syenite rocks, the most usual primary occurrence in all these countries 

 is in pegmatite veins in granite, especially in those characterised by 

 the presence of much albite. In these veins they are commonly ac- 

 companied by quartz, orthoclase, and mica, as well as albite, whilst 

 garnet, zircon, topaz, monazite, cassiterite, and other uncommon 

 minerals are often present. The only primary deposits described so 

 far in Australia are those of Finniss Eiver (Northern Territory), Green- 

 bushes (Western Australia), and the Wodgina District (Western Aus- 

 tralia), all areas of granitic rocks. 



