70 GEOLOGY OF MOOSE RIVER GOLD DISTRICT — WOODMAN. 



It is most abundant in the last named situation, belonging very 

 evidently to the upper of the two layers, and becoming gradu- 

 ally less abundant upward. Often at the top and immediately 

 below the division plane, crystals are en irely absent. This is 

 well shown in the quarry on areas 73 and 74, especially along 

 the south side. In the small quarry on area 75, some of the 

 strata have the greatest accumulation of pyrite along a medial 

 plane, decreasing upward and somewhat less downward, with 

 still a layer between the beds. The grouping of pyrite along 

 the stratification planes is so constant in the slate, that in many 

 other parts of the country, where layers are too similar to give 

 the usual criteria of color and texture, and where bedding is 

 obscured by strong cleavage, it has been possible to use planes 

 of pyrite crystals with complete success in interpreting structure. 

 Attitude in leads and cross veins. — In the veins the mineral 

 is abundant but often erratic in distribution, in places pro- 

 truding into the quartz from the sediments. Within the vein it 

 is irregular, and never occupies a definite central position. Its 

 most important place, and commonest, is on the margins of the 

 veins in sheets. While these are found on both sides, they are 

 much more abundant on the hanging walls. This is brought 

 out well in the zone of oxidation, by the rusting of the iron ; 

 below it is as real, but less apparent. The hanging wall lead of 

 the Jo. Taylor belt, on areas 73 and 74, shows this. The rule 

 does not hold in the irregular cross veins, 



ARSENOPYRITE. 

 This occurs sparingly in the slate, abundantly in the whin, 

 and in the veins is erratic in distribution but present in spots in 

 considerable quantities. In the two first mentioned it is crystal- 

 ized ; in the last, massive except in a few instances. Very 

 rarely a short vein is found composed entirely of a mixture 

 of pyrite and arsenopyrite, but in Moose River these are of small 

 size. In the sediments it is so rare in the slates as to be unim- 

 portant. Where present it is either in the stratum, or in a few 



