BY L. A. COTTON. 817 



basalt, considerably less than an acre in extent, still remains. 

 The discovery of diamonds here is only of importance, for the 

 purpose of this paper, as a piece of evidence as to the course of 

 the lead. 



At Collas' Hill, diamond-bearing drifts have been worked with 

 some success. Here, the basalt has been intersected by the 

 present stream-course, and has exposed the Tertiary gravels on 

 the side of a hill. These deposits were prospected by means of 

 tunnels, driven at the level of the wash, which stands at an 

 elevation of about 2,280 feet. The diamonds found here aver- 

 aged about four to a carat, and contained a number of triangular, 

 flattened crystals. 



The Streak of Luck Mine is situated on the next remnant of 

 tlie Tertiary lead. Here the basalt has been entirely denuded, 

 and the gravels lie either exposed at the surface, or buried under 

 a few feet of alluvial. The level of the wash at this mine is 

 about 2,250 feet. The diamonds from this locality averaged 

 about four to the carat. 



The Deep Shaft Mine adjoins the lease just mentioned. The 

 diamond-bearing drifts are here covered by basalt, varying in 

 thickness from 50 to 130 feet. This has been one of the most 

 productive mines on the field. A small tributary from the south- 

 east joined the lead at this point. This has introduced, into the 

 lead, boulders of clay-slate from a small area of this rock about 

 half a mile distant. In places, these boulders are several feet in 

 diameter, and overlie the sandy drift. The wash is normally 

 about one foot in thickness, and is covered by sandy drift, the 

 grainsize of which is from 3 to 6 mm. The diamonds occur in 

 the wash, and are associated with quartz, topaz, tourmaline, 

 garnet, sapphire, zircon, and tinstone. The gems are found 

 unevenly distributed, often occurring in clusters where concen- 

 tration has taken place. It is recorded that 150 carats have 

 been recovered from a single load of wash-dirt. It is noteworthy, 

 that the diamonds won from this mine are larger than tiiose from 

 the lead above this place. The stones average three to the carat, 

 and are of good quality. From 40 to 50 per cent, of the stones 

 are white, rather more are a light yellow, while a few are brown 



