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producing planes along which fracturing took place. By 

 far the greater number lie on the foot-wall with only a thin 

 film of crushed slate or gouge separating them from the 

 quartzite. Occasionally, the quartz is "frozen" to the 

 wall. 



As a rule the veins are quite conformable with the strata, 

 but occasionally they pass from one wall to the other. 

 A saddle-vein may have one leg on the footwall and the 

 other one on the hangingwall. On a smaljl crumple, the 

 vein may lie on the footwall of that part above the crumple 

 and on the hanging wall in that part below, forming 

 irregularly shaped veinlets and quartz masses scattered 

 all through the slate belt where it passes from one wall 

 to the other in the short limb of the crumple. Some veins 

 bifurcate, and one portion passes to the hanging wall, 

 while the other remains on the footwall. 



Some slate beds are found to carry several quartz veins, 

 generally conformable with the strata, and constitute 

 those large bodies of low grade ore, often 5 to 20 feet (1 • 5 to 

 6 m.) thick, that have of late years been worked with profit. 

 These deposits are designated "belts", while the well- 

 defined vein is designated a "lode" or "lead". The belt 

 is sometimes also composed of a network of veins, the 

 veinlets following the bedding planes for short distances 

 and then crossing obliquely to join other veinlets. 



Corrugated Veins. 



Interstratified veins often exhibit a remarkable folded 

 or corrugated structure within the beds of slate that 

 contain them. The corrugations, or crenulations, usually 

 occur at or near the apex of the anticline and sometimes 

 in the syncline, and run parallel with one another and in 

 a direction approximately parallel with the axis of the fold. 

 At the apex of the fold, the corrugations dip with the dip 

 of the strata, which then corresponds to the pitch of the 

 fold, but on each side of the apex they radiate more or less 

 from the centre. The amplitude and interval of the folds 

 generally vary with the thickness of the vein and of the en- 

 closing bed of slate. Also the nearer the veins lie to the anti- 

 clinal axis, the more pronounced these corrugations become. 

 In some veins the folding has been so intense as to separate 

 the quartz with disconnected rolled portions. The name 

 "barrel" quartz has been given to the larger corrugations, 



