520 THK ORK-DEPOSITS OF BORAH CHKKK. 



LLL, line of lode - FFF, line of fault— M, Moore's Shaft— D, Davis's 

 Shaft— C, Cjnrad Shaft —7, winze — 5, winze — A, Alwell's Shaft. 



Fig. 2. —Three specimens illustrating extent of the metasomatic replacement 

 of quartz by sphalerite. 

 A, massive quartz with one hexagonal crystal, replaced by sphalerite — 

 B, more advanced stage of metasomatic replacement — C, stage of almost 

 complete replacement; only a few quartz crystals unattacked. 



(Two-thirds nat. size.) 



Plate xvi. 



Portion of Conrad Lode illustrating banding. 



A, pyrite and chalcopyrite with quartz — B, sphalerite, with quartz-seams 

 — C, galena — D, quartz. 



(Two-sevenths nat. size.) 



[Printed off September 15th, 1910]. 



