COMPOSITION OF VEIN MATERIALS. 



557 



only accessory constituents in either ore or vein material. The composi- 

 tion of some of the typical forms of vein material, taken from Table X, 

 Appendix B, is given below. 



Vein materials. 



80s 



"SiOz 



No. 1 is a cavernous red rock, with slightly greasy luster, which, though 

 containing only a trace of lead carbonate and too little silver to pay for 

 working, is yet classed as "hard carbonate" from its outward appearance, 

 this miner's term being quite elastic in its application. It is mainly silica, 

 combined perhaps in part with oxide of iron. Rock from this same mine, 

 of quite similar appearance, but with a few delicate crystals of cerussite 

 and horn silver lining the cavities, constitutes a very rich ore. 



No. 2 is a dark-colored "iron ore," intermediate between the black 

 iron and the jaspery iron of the Fryer Hill mines. It contains a rather 

 unusual percentage of zinc, and its silica contents are much lower than 



