80 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. 



shown by the analysis, which seems to have arisen from imperfect desic- 

 cation. 



A second separation was nndertaken with No. 21!), Sulphur Bank, a 

 rock composed chiefly of greenish zoisite and actinolite, the former em- 

 bedded in the latter. It was impossible wholly to separate the two minerals 

 and the purest sample had a specific gravity of no less than 3.37, show- 

 ing that much actinolite remained. The analysis gave the following 

 i-esults: 



Loss above 100°, H-0 1.119 



Silica, SiO- 39.196 



Phosphoric jicitl, P-0" Trace 



Titanic acid (rutile), TiO- 1.169 



Alumina, Al-C 22.760 



Ferric oxide, Fc-O' 6.487 



Ferrous oxide, FeO 1. 783 



Nickel oxide, NiO Trace 



Manganous oxide, MnO 0.090 



Lime, CaO -22.023 



Magnesia, MgO 1- 643 



Soda, Na^O 3.382 



Potassa, K-0 0.575 



Total 100.227 



This analysis gives the atomic ratio H- : R" : R" : Si — 0.57 : 4.56 : 

 7.22 : 12. Here, also, if the admixed silicate has a protoxide base and if 

 it contains about one-sixth of the silica, the ratio is reduced to one resem- 

 bling that of zoisite, viz, § : 4 : 9 : 12. In this case there is too little 

 water instead of too much, but in performing the analysis the sample was 

 accidentally dried at somewhat above 100°. 



Althouo-h zoisite is extremely abundant in the metamorphic rocks of 

 California, there were no specimens which seemed so well adapted to a 

 separation as the two discussed above. The manner in which the compo- 

 nents of these rocks are intergro wn renders separations almost impracti- 

 cable. Impure as the materials analyzed were, however, the results show 

 that the substance in question was really a zoisite. 



Under different conditions zoisite possesses a considerable similarity 

 to other minerals. Especially when granular, it might at first sight be 

 confounded with epidote ; but it is distinguished by its color, its mono- 



