PROCEEDINGS OF SECTION C. 443 



Most native tantalates and niobates offer considerable resistance 

 to chemical change, and, being in the main both hard and tough, are 

 of frequent occurrence in detrital deposits, though usually overlooked 

 unless the latter happen to be worked for gold or tin. Still, there are 

 numerous records of their detection in stream deposits in America, 

 Siberia, and England, whilst detrital ores are of great importance in 

 North- Western AustraUa. 



Within the last two years the search for these minerals has been 

 greatly stimulated by the fact that they have suddenly become of 

 considerable commercial value. This has been largely due to the dis- 

 covery of the tantalum electric lamp, but partly also to the experiments 

 being made with tantalum-steel alloys, which appear to possess many 

 valuable properties. As much as 20s. per pound was paid in 1905 for 

 bulk lots of high-grade tantalum ore. The price has, however, been 

 very variable lately, ranging from about £200 to £1,000 per ton. 



Queensland. — Geraldton. — The only record of any tantalum in 

 this State is contained in publication No. 196 of the Geological Survey. 

 A black sand occurring on the shore at the mouth of the Johnstone 

 River, near Geraldton, was found on analysis to consist mainly of 

 ilmenite (84 per cent.). With it was 0-78 per cent, of combined niobic 

 and tantalic oxides, equal to 0-95 of tantalite or columbite. Which 

 of these latter minerals was present is doubtful, as no separation of 

 the oxides was made. The only other rarer minerals present were 

 monazite and zircon. 



According to the 1902 geological map of Queensland, the watershed 

 of the Johnstone River is occupied mainly by crystalline schists, with 

 smaller areas of basalt. It is probably from the former — which may 

 include granitic schists — or from offshoots of the large masses of granite 

 lying further to the north and west, that the tantalite has been derived. 



New South Wales — Ballina. — In volume VII. of the Records of 

 the Geological Survey of this State there is a description of some tan- 

 taliferous concentrates from Broken Head, near Ballina. The original 

 beach sand from which these were obtained was composed of quartz, 

 zircon, ilmenite, with smaller proportions of monazite, cassiterite, 

 iridosmine, and gold. The concentrates consisted of — Monazite, 65 

 per cent. ; zircon, 22 per cent. ; cassiterite, 9 per cent., and carried 

 1-10 per cent, of tantaUc oxide in one case and 0-86 in another, equal 

 to between 1 per cent, and 1^ per cent, of tantalite. 



Euriowie.—ln the early nineties Mr. C. W. Marsh reported the 

 occurrence of columbite in association with cassiterite at the Euriowie 

 Tinfield, near Broken Hill. A small specimen of this columbite, about 

 2in. long and fin. square, is in the Geological Museum in Sydney. It 

 is too small to permit of an exact analysis being made, and there is 

 some slight doubt as to whether it may not be euxenite (niobate and 

 titanate of yttrium, &c.). Its specific gravity is said to be about 6, 

 which supports the theory that the mineral is columbite. The tin lodes 

 at Euriowie, according to Mr. Pittman, consist of a series of coarse 

 pegmatite dykes, traversing gneiss and mica schist. The dykes are 



