390 ZINC AND LEAD DEPOSITS OF BROKEN HILL. 



H. U. Moffat, J. L. Pophani, J. Teagle, and Franklin White. 

 To Mr. H. S. Mc\'ey the writer is indebted for drawing the 

 diagrams which accompany this note. The photographs wer^ 

 kindly lent for reproduction by Mr. Franklin White. 



II. Geology of the Deposits. 



The country in which the deposits are situated is fairly 

 flat exce])t for a series of small kopjes (named Nos. i. 2, 3, 4) 

 and one or two others. These kopjes consist, in some 

 instances entirely, and in others in large part, of the oxidised 

 compounds of zinc and lead and iron.* ( See Plate 4, upper 

 photograph. )t 



The mining development work carried out consists| chiefly 

 several directions and at several levels ; from these are put out 

 a number of cross-cuts. A few rises between the levels and 

 several small winzes exist, also, several shafts are sunk from 

 the surface of the kopjes and between them; in the kopjes 

 several large quarries and benches have been made. In Kopje 

 Xo. I an incline passes down to water-level, where a drive exists, 

 and from the drive which extends from end to end of the kopje 

 two cross-cuts are made ; one of these opens into the lower 

 part of the bone cave. Nearly all the workings, therefore, are 

 in the oxidized zone, which has thereby been particularly well 

 exposed. 



The accompanying geological sketch-map (Fig. i) is very 

 rough, but serves to give a general idea of the geology. The 

 rocks appear to be highly inclined or vertical and to be striking 

 about east and west. 



In making a traverse from south to north the following 

 rocks are observed : — 



(a) Limestone. 



(b) Phyllite (disturbed and contorted in places), 

 passing insensibly to 



(c) Limestone (largely dolomitic).§ 



(d) Conglomerate. 

 (c) ?Phyllitic grit. 



The rocks are members of an ancient schistose sedimentary 

 group, perhaps of the same general age as those occurring in 

 Matabeleland, but probably considerably younger. 



No. I Kopje is situated on the limestone (c), and near '>t 

 are the smaller kopjes 3, 4, etc. No. 2 Kopje is situated alone 

 about half a mile S.S.E. of No. i, partly in the limestone (a) 

 and partly in the phyllite (b). 



* White, loc. cit., voL vii., p. 14. 



t The upper (smaller) photograph is a view of " Kopje No. 1 "; the gossan of 

 a deposit, containing the bone cave. The lower (larger) photograph is a view of 

 the east side of that kopje, shewing the cavernous nature of surface ore. and posi- 

 tion of a bone deposit (left-hand lower corner of photograph) at the east end of 

 water-level drive. 



+ White, loc. cit., vol. vii., pp. 14-18. 



§ Mennell and Chubb, loc. cit., p. 445. 



