DEPOSITION OF CINNABAR. 437 



specimens from Huitziico, in Mexico, wliich also seem to indicate a transfor- 

 mation of metaeinnabarite into the red sulpliide by the action of solvent 

 flnids (see page ID). The mercury found at the (Ireat GcN'ser of Iceland is 

 also surrounded by black sulphide, which at a greater distance from the 

 metallic globules passes over into the red modification. 



While dilution will produce metallic mercury and a causa vera of its 

 existence is thus detected, there may Ije other ways besides this in which 

 it is produced in nature. Thus sulphydric acid precipitates a mixture of 

 quicksilver and mercuric sulphide from mercurous salts. Wiiether soluble 

 mercurous salts can occur in nature, excepting near the earth's surface, is 

 another question. But even liglit is well known to decompose this feeble 

 sulphide, and it is not inqiossible that the decomposition of organic matter 

 associated in most cises with cinnabar deposits, and which seems to be 

 especiall3' abundant in those mines in which metallic mercury most prevails, 

 may lead to the isolation of metallic mercury. 



Conclusions, — The couditious of the solution and preci})itation of ores 

 traced in this chapter appear beyond doubt those mainly instrumental in 

 forming the deposits of Steamljoat Springs and Sulphur Bank. Most of the 

 other quicksilver mines in California show ores and gangue minerals of 

 similar composition to these, and many of them are accompanied more or 

 less closely by warm springs containing much the same salts in solution. 

 Some of the gold veins also appear to bear so considerable a resemblance 

 in many particulars to these deposits as to lead to the belief that they too 

 were formed by precipitation from solutions of soluble double sulphides. 



That pyi'ite, gold, and other ores are sometimes produced in nature by 

 other methods is absolutely certain, for some auriferous pyrite is known to 

 have resulted from tlie reduction of iron sulphate by organic matter. This 

 particular process is probably confined to .short distances from the surface, 

 for I know of no indication of the formation of iron sulphate far from the 

 oxidizing influence of the atmosphere. But there may be other solvents 

 yet for these and other minerals which can form at great depths, and, if 

 such there be, I am convinced that there are cases in which these solvents, 

 and not those which it has been my good fortune to trace in the foregoing 

 pages, have been instrumental in the segregation of oi'es. 



