348 N. R. J tinner : 



Dyke Veins. — These are the most persistent and by far the most- 

 important economically of the reefs near Diamond Creek. Gener- 

 ally two well-defined reefs occur : — 



1. Hanging wall reef. 



2. Foot wall reef. 



Besides these, others are occasionally present, and sometimes one 

 reef will split into two, and the i:)arts may junction again to form 

 the main reef. In general these reefs are approximately parallel 

 to the Avails of the dyke, and it is only on rare occasions that 

 a quartz-reef cuts the dyke transverseh'. The reefs are generally 

 within the dyke, sometimes as much as six feet, but generally only 

 about twelve inches. An inch or so of pug sometimes accompanies 

 these reefs and striae and slickensides are often present. The 

 thickness of the reefs varies considerably, from a mere thread t& 

 two or three feet. The reefs, when they occur at the junction of 

 the dyke and the shales, are usually smaller than the average, 

 and sometimes they split up into a number of leaders, running out 

 into the country. 



Joint Plane Reefs. — These are not of any economic importance. 

 They occur typically in the 600 feet level south. Here one section 

 shows one of these reefs displacing a tongue of the dyke, and there- 

 fore they are later in age than the dyke. 



(b) Fissures and their origins. 



1. The dyke fissures. The frequent association of the dyke veins 

 with a little flucan. and the striae on the dyke walls between the 

 dyke and the quartz are suggestive of movement. The direction of 

 the striae is generally, l)ut not always, in that of the dip of the 

 dyke, and having no north or south component. One very good 

 example of these striae occurred on the footwall of the dyke in the 

 stopes al)ove the 800 feet level, where tlie (juartz had been broken 

 out. Two sets of striae "were present, the Hr.st consisting of coarse 

 rfor]-ugati()iis. having no meridional component, and the second set 

 ■were later, and very fine, and pitched to the south. The (piestion . 

 is whether these movements occuiicd In-fore the formation of the 

 reefs or after. Rarely the striae aie also on the ([uartz, indicating 

 that the nioven'iont iii part at l(>ast was later than the formation of 

 the reefs. The writoi- bclirvi's that the ri'cfs ari' tilling contraction 

 joints whicli are roughly i)aiallel to the Avails of the dyki-, and that 

 movement has occurred both before the formation of the reefs and 

 for a AA'hile, after the ore had formed, .\ci-ording to this vicAv the 

 fissures are essentiallv neither eoniraetion tissuies nor iissures of 



