AND ASSOCIATED EOCKS OF THE SOUTHERN TRANSVAAL. 415 



A drill-hole placed on ' Block B, deep level ' reached a depth of 

 800 feet without striking any reef, the cores showing a schistose 

 material with much iron pyrites. Another drill-hole in the Vogel- 

 struis property (see Map, PI. XI.) after passing through about 

 60 feet of the altered surface-rock, entered a bluish schist which 

 continued for a depth of over 100 feet, when a diorifce dyke was 

 struck. The depth ultimately reached by the drill-hole was 423 feet, 

 several layers of white crystalline quartz being passed through. 

 Both in this quartz, and in the quartzite, crystals of iron pyrites 

 were exceedingly numerous. 



Erom the E-obinson Mine to the Bantjes Mine an average dip of 

 45° prevails ; from the latter to the Kimberley Roodeport Mine the 

 average dip is 70°, and thence to the Banket Mine the dip gradually 

 decreases until at last it is only about 15°. At the Banket Mine 

 the reefs suddenly assume a northerly strike (see Map, PI. XI.) ; a 

 deep gully then intervenes, on the opposite side of which the reefs 

 cannot be traced. 



(c) The Main Reef Series east of the Salisbury Mine. 



East of the Salisbury Mine we meet with much the same varia- 

 tion in the disposition of the reefs as in going west. In several of 

 the mines we have more reefs below than are found at the surface. 

 In the Jumpers Mine, 3 miles east of the Salisbury, three reefs are 

 found. The dip between the two mines is never much less than 

 70°, the strike being nearly due E. and W. At the Jumpers Mine 

 a break occurs, and the dip to the east is found to have decreased to 

 45°. The dip is still further lowered in the Simmer and Jack Mine 

 to about 10°, after which it again increases ; but, so far as the 

 writer is aware, it never goes beyond Qo°. East of the Jumpers 

 Mine the strike has a slight northerly trend. 



East of the Simmer and Jack Mine the distinction into ' north,' 

 ' main,' and ' south ' reefs vanishes. Several reefs are found, but 

 in composition they differ somewhat from those of the Main 

 Eeef Series, and resemble more closely those presently to be de- 

 scribed as lying* to the south. In the United Main E-eef Company's 

 Mine a reef has been struck at a depth of 100 feet, which is a true 

 conglomerate dipping at about 64° S.S.W. Immediately below is a 

 band, a few inches in thickness, of glossy black shale. The cement- 

 ing-material, or matrix of the reef, is very much greyer than that of 

 any of the conglomerates of the Main Beef Series, and a few pebbles 

 or fragments of black shale like that lying below are met with. 



In the Cinderella Mine (see fig. 3, p. 416), a little north of Boks- 

 burg, a conglomerate or reef striking nearly N.E. and S.W. is worked 

 for gold. Immediately beneath it is a blue slaty shale about a foot 

 thick. The surface of the pebbles in the conglomerate is of a rich 

 peacock-blue colour due to a coating of an oxide of iron. East of 

 Boksburg the reefs are soon cut off by a large mass of diorite. 



So far as the writer has observed, the thinning out and partial 

 disappearance of some of the reefs is quite as common to the east 



2g2 



