68 GEOLOGY OF MOOSE RIVER GOLD DISTRICT — WOODMAN. 



Details of contacts. — It is chiefly in connection with corru- 

 gations that we often find the leads very laminated, the layers 

 consisting of alternate bands of slate and quartz. Usually the 

 laj^ers of the latter are thick, of the former thin ; but occasion- 

 ally the reverse is true. The quartz in these laminse is never 

 cellular, and is generally dark and translucent. It is noticeable 

 that the crenulation and rolling are accompanied by many frac- 

 tures, upward from the crests and downward from the troughs ; 

 and that very rarely are these occupied by gangue, or by pyrite. 



In close detail, the margins of the leads are seen not to follow 

 the stratification, either in portions that are straight or in rolls. 

 Some of these contacts are shown in photograph on pi. 14. 

 Frequently in detail the vein breaks up into two or more string- 

 ers, or dies out and is replaced by another en echelon. In many 

 specimens laminae of slate are seen, wholly or partially detached^ 

 and thinning out rapidly to an edge. Several of these slivers 

 may lie in close proximity in the lead. On the outside of the 

 curve of rolls and other corrugations, the country rock gapes 

 more or less, and into these fissures the vein material has pene- 

 trated ; but this occurs also where the stratification is not curved. 



In the slides all these features, and indeed several more, are 

 shown in a very minute way, proving that in the finest detail 

 the contacts have the same characters as on a larger scale. 



RATIO OF VEIN MATERIAL TO SEDIMENTS. 



In most fields and most parts of this field, isolated outcrops 

 give a minimum amount of vein material in sight, across the 

 strike of the folds. In the central belt here, in which the three 

 trenches and large quarry were cut in or near 1899, continuous 

 exposures give a maximum of quartz, under exceptionally favor- 

 able conditions for the formation of veins. In this zone, south 

 of the north anticlinal axis, I have counted and measured 70 

 leads, in a distance of 750 feet, aofcfreofatincf 800 inches in 

 breadth of vein material. This gives 1 to 30 in cross-section — 

 an extremely small amount. Yet this is higher than any 



