ZINC AND LEAD DEPOSITS OF BROKEN HILL. 397 



viciiiitv of the bone deposits, with the exception of one 

 or two insigniticant occurrences which may be explained by 

 the movement of the phosphoric acid in solution from its source 

 of origin. The origin of the phosphate minerals occurring in 

 Kopje Xo. I is therefore evident, namely, the reaction of phos- 

 phoric acid supplied by the leaching of the animal remains with 

 the oxidized zinc and lead compounds. On Kopjes Nos. 2 and 3, 



Fig. 4. 



Diagrammatic Plan ok "Kopje No. .2," 



Shewing roughly the distribution of Tarbuttite and Pyromorphite in Drives and 



Cross-cuts. 



t = Tarbuttite 

 py = Pyromorphite 



in both of which phosphate minerals are present, the evidences 

 of the occupation of small ledges and crevices by man or beast or 

 both are found. In Kopje No. 3. for instance, a large cavernous 

 ledge between craggy walls is about 30 feet by 12 feet, narrowing 

 at one end. Its floor, on which white quartz chips abound, 

 consists of several feet of whitish, soft material full of pebbles. 

 Further opening up of the deposit in Kopje No. 2 may almost 

 certainly reveal the presence of a large bone deposit close to 

 (probably above) the large phosphate zone which has been 

 exposed in the drives. 



Secondly, it is most interesting that the vanadium minerals 

 are not found excepting close by, generally actually with, the 

 phosphates. This is especially to be noted in the western group 

 of Kopjes (Nos. i and 3). Conversely, most of the phosphate 

 mineral occurrences known at Broken Hill have vanadium 

 minerals either in actual contact or in close proximity. This 

 seems to be important and suggestive when it is remembered 

 that the element vanadium is one of a group — a'^senic, phos- 



