SUMMARY. 393 



angle of from 33° to 45°. Near tlie top, in most of the sections, one or more 

 secondary fissures diverge from the main Lode and penetrate the east wall, 

 thus cutting off a body of country rock, or "horse," which is approximately 

 triangular in cross-section. This horse is of variable vertical and horizontal 

 dimensions, and often divided by sheets of clay or quartz. Below the horse 

 the vein is for the most pai't narrow. 



The walls. — Tho hanging wall of the Lode between the points at which 

 it branches is older diabase, which also extends some distance on the south- 

 east branch towards the Justice, and towards the Scorpion on the northeast 

 branch. Its limits in the latter direction are unknown. Almost all of this 

 diabase is in an advanced stage of decomposition. The foot wall of the 

 main fissure is granvilar diorite, except in Gold Hill, where this rock is re- 

 placed by metamorphic slates, and is much less decomposed than the hang- 

 ing wall. The northern and southei-n branches of the vein pass through or 

 along the contacts of various older rocks. The black dike or younger dia- 

 base appears in the Savage and Hale & Norcross, but not to the north of these 

 mines, and has been followed on or near the foot wall to the fork at the 

 Overman, and thence in a southwesterly direction toward American Flat. 

 It is the behavior of the two diabases which has given rise to this fork, the 

 older diabase forming the hanging wall of the easterly branch for some dis- 

 tance from its origin, while the narrow dike of the j^ounger variety marks the 

 course of the westerly vein. To the north also there are indications that 

 the direction of the branches was predetermined ; the northeasterly one by 

 the contact between diabase and diorite, and that which has Ijeen explored 

 in the Sierra Nevada and Utah mines by the presence of metamorphic rocks 

 and some intrusive stringers of diabase. 



Contents of the vein. — TliB couteuts of tho vciu is simj^lc ou the whole. 

 Besides fragments of country rock, practically the only gangue which it 

 contains is quartz; though calcite occurs in insignificant quantities in the 

 main Lode, and is the prevalent mineral in the Justice. The principal ore 

 is argentite, accompanied by gold, probably in a free state, though sulphur 

 salts occasionally form rich stringers and pockets. The distribution of ore 

 is very variable. That associated with the diorite carries a little gold and 

 almost no silver, while that associated with diabase is regarded as a silver 



