March 3, 192 1] 



NATURE 



n 



A New Deposit of Cobalt Ore. 



THE development of new uses of metallic cobalt 

 has established a demand for this com- 

 modity, which until recently was a metal of 

 comparatively small account. When the production 

 of metallic cobalt as a by-product commenced a few 

 years ago, it was necessary to initiate research into 

 the possible uses of the metal before an increased 

 demand could be created. The position now is that 

 the uses of cobalt are many and various, and the 

 question is : Where are we to find the supplies that 

 are likely to be necessary to meet the future demand 

 for the metal? 



In these circumstances it becomes important to put 

 on record any discoveries of new occurrences that give 

 any promise of development to meet the world's 

 requirements, and in this connection a report by the 

 Queensland Government Geologist recently received 

 at the Imperial Mineral Resources Bureau concerning 

 a high-grade deposit near Selwyn, in the Cloncurry 

 district of Queensland, is of special interest. The 

 locality is approximately 19 miles south of Selwyn, 

 the nearest railway station, which is 71 miles from 

 Cloncurry. By track it is about 5I miles south of 

 •Mount Dore (located on Queensland 4-mile map- 

 sheet 120) and 1-2 miles west of the Mort River. 



The cobalt ore occurs at the contact of diorite 

 (apparently a dyke about 5 chains wide) and schists, 

 the latter belonging to the Cloncurry series of sup- 

 posed Silurian age. The schists have a strike of 

 5° west of north, and dip easterly at angles of 74° 

 to 80°. They form noticeable outcrops on the area, 

 and associated with them at a few chains from the 

 diorite are several prominent white quartz outcrops 

 conforming to the strike of the country, and to all 

 appearances barren. 



The workings at present consist of four shafts. 

 No. I is 23 ft. deep. No. 2 27 ft.. No. 3 20 ft., and 

 No. 4 20 ft. The distance between No. i and No. 4 

 shafts is 300 ft. 



The ores consist of cobaltite (sulpharsenide of 

 cobalt, containing 355 per cent, of cobalt) and 

 erythrite or cobalt bloom (hydrous arsenate of cobalt, 

 containing when pure about 2q per cent, of cobalt). 

 A picked sample of cobaltite from this lode recently 

 assayed for the Department of Mines gave the fol- 

 lowing composition : 



Per cent. 



Arsenic ... ... ... ... 402 



Sulphur ... ... 15-8 



Cobalt ... ... ... ... 33-1 



Nickel nil 



Iron ... ... ... ... ... 2-1 



Insoluble (chiefly SlO^) 8-3 



995 



The workings are not extensive, and the following 

 notes are descriptive of what work has been done in 

 prospecting : 



¥lo. I Shajt. — This is the most southerly shaft on 

 the lode. At the top the lode is 2 ft. 6 in. wide, and 

 at the bottom (23 ft. deep) it has narrowed to 12 in. 

 On the hanering wall there is a seam of white clay 

 up to 4 in. thick. Where this is removed the hanging 

 wall is pink-stained with "bloom." The footwall 

 has a smooth surface indicating a fault plane. The 

 ore here consists of highly altered rock with veins 

 of erythrite and small lenses of sulphide, 

 ^ An average sample chipped across the lode on both 

 sides of the shaft (i ft.* on the north and 6 in. on the 

 south) near the bottom gave the following analysis 

 (Assay No. 515/7) : 



NO. 2679, VOL. 107] 



Gold 

 Silver 



Metallic cobalt 

 Metallic nickel 

 Arsenic 



9 grams 



trace 



17-4 per cent. 



nil 



9 per cent. 



]>io. 2 Shaft. — This shaft discloses a lode forma- 

 tion 5 ft. wide regularly to the bottom, depth 27 ft. 

 Both walls are well defined. On the footwall is a 

 seam of solid sulphide ore 2-9 in. thick, and on the 

 hanging wall there is a very narrow seam of sulphide. 

 Between tw'o walls the lode material consists of a 

 siliceous indurated gangue, much jointed, with 

 erythrite and sulphide veins coating all the joint- 

 faces. Cobaltiferous wad is present in small quantities 

 in the lower half of the shaft, associated with the 

 two other minerals. A grab sample from the ore- 

 paddock at this shaft returned (Assay No. 516/7) : 



Gold 

 Silver 



Metallic cobalt 

 Metallic nickel 

 Arsenic 



19 grams 



trace 



12 per cent. 



nil 



16-5 per cent. 



The ore-paddocks at this shaft are estimated to 

 contain 50 tons of ore, averaging, as above, approxi- 

 mately 12 per cent, of cobalt. 



No. 3 Shaft. — ^The lode varies from 2 ft. to 3 ft. in 

 thickness. On the footwall is a very thin seam of 

 scheelite. The lode is schist much altered and re- 

 placed by veins of erythrite, generally not exceeding 

 I in. thick. There are small lenses of sulphide close 

 to the footwall. 



No. 4 Shaft, the most northerly, has turned out 

 the most massive' sulphide ore. The lode is from 2 ft. 

 to 3 ft. wide, and consists of soft, decomposed schist 

 largely replaced with erythrite. It contains a central 

 string of solid sulphide ore in the form of lenses 

 almost constituting a single vein. The lenses vary 

 from 8 in. to 18 in. in width. Analyses of the fol- 

 lowing samples were as follows : 



Average Sample taken across Lode in No. 4 Shaft 

 {Assay No. 513/7). 



Gold 2 dwt. 19 gr. 



Silver 18 dwt. 



Metallic cobalt 195 per cent. 



Metallic nickel nil 



Arsenic 28-3 per cent. 



Average Sample of Paddock of Oxidised Ore 

 (Assay No. 514/7). 



Gold trace 



Silver trace 



Metallic cobalt 10 per cent. 



Metallic nickel nil 



Arsenic ... • 12 per cent. 



The ore-paddock near this shaft is estimated to 

 contain 32 tons of picked high-grade sulphide ore, the 

 approximate content of cobalt equalling 25 per cent. 

 There are also about 10 tons of lower-grade oxidised 

 ore consisting mostly of erythrite in a schist gangue 

 assaying 10 per cent, of cobalt. 



It is estimated that in prospecting the lode between 

 130 and 140 tons of ore have been raised, of which 

 92 tons represents ore in paddocks ; 30 tons of the 

 latter is approximately of 25 per cent, grade and the 

 balance of 10-12 per cent, grade. 



The lode is regular in its trend, almost following 

 a straight line for at least 300 ft. The walls in places 



