448 PROCEEDINGS OF SECTION C. 



In a recent article in the Mining Journal, Messrs. F. H. and W. A. 

 Mitchell (the latter assayer at the Mons Cupri Copper Mine, 80 miles 

 from Wodgina) make the following statement with regard to the first 

 discovery of tanta'um ore at Wodgina : — " This mineral was first 

 observed by us in North- West Australia early in 1901, when a crystal 

 was submitted to the British Museum authorities for confirmation ; 

 but it was not until about four years ]ater that we introduced this 

 mineral into Europe for commercial purposes." 



In May, 1904, a black mineral from this locality was forwarded 

 for identification to the Acting Mineralogist and Assayer, Mr. C. G. 

 Gibson, and proved to be manganotantalite, a preliminary analysis 

 showing the presence of 80 per cent, of tantalic and niobic oxides and 

 16 per cent, of manganese oxide. At that time there was no market 

 for the mineral except for museum and other educational purposes, 

 for which purpose the demand was limited to a few pounds per annum. 

 Towards the end of the year, however, the demand which arose in con- 

 nection with the manufacture of tantalum lamps stimulated prospecting 

 for these minerals, and since then a gTeat number of ores from all parts 

 of the district have been examined in the laboratory attached to the 

 Geological Survey of Western Australia. 



The locality has recently been geologically examined and mapped 

 by Mr. Maitland, and from his report the following resume of the 

 structural features of the rock masses and ore bodies has been culled. 



The tantalum ores occur in stream deposits, in shallow surface 

 detritus in the immediate vicinity of the outcrops of pegmatite dykes, 

 and in these dykes themselves. They occur in a mass of hornblende- 

 schist, and are apparently offshoots of a mass of granite lying at a short 

 distance to the north, east, and south-east. Between the hornblende 

 rock and the granite on the south-east are a series of schists of in- 

 determinate origin, mostly very siUceous and carrying either mica or 

 haematite. Their origin is still a matter of some speculation. Within 

 the area of these schists the pegmatite veins are tin-bearing, and are 

 being worked for that metal. 



The most important tantalum vein in Wodgina proper is that which 

 passes through mining leases 86 and 87 in a north and south direction. 

 It is from 30ft. to 40ft. wide, and consists of variable proportions of 

 quartz, felspar (mainly albite), mica (muscovite and lepidolite), and tan- 

 talite ; the last-named in crystalline masses from the size of shot up to 

 5cwt. in weight. A little west of this main vein is a second smaller one 

 of similar nature. From the outcrops of these veins a larger amount of 

 ore has been shed, and the greater part of the ore hitherto exported has 

 been obtained by " specking " and dryblowing the shallow detritus on 

 the surface. About 71 tons is said to have been obtained in this way. 



The main vein appears to continue for about a mile north, where 

 it is 20ft. wide, and has there also been worked for tantalum. 



Since Mr. Maitland reported on this field other tantalum-bearing 

 dykes have been opened up in the vicinity, and ore is still being obtained 

 from shallow surface soils, as well as from true alluvial deposits in the 

 many small valleys. 



