SUMMARY. 471 



mine. There is no lava in the neighborhood. In the Stayton mines, San 

 Benito County, large quantities of stibnite were associated with cinnnbar. 

 The Oceanic, in San Luis Obispo County, is in unaltered sandstone, sup- 

 posed to be Miocene. Most of the other deposits occur in shattered rock 

 masses of the Knoxville group, forming stockworks. In some cases they 

 seem to bo accompanied Ijy true veins, and sufficient exploration would 

 doubtless show a fissure system connected witli each of them. The u.sual 

 mineral association is the same so often described above. 



On the gold belt of California cinnabar occurs in pebbles, in aurifer- 

 ous gravels, and in true gold quartz veins, so that there are mercuriferous 

 gold veinsi as well as auriferous deposits of cinnabar. In the Barcelona sil- 

 ver mine, Belmont, Nev., cinnabar ^vas found with silver ore in the vein. 

 Cinnabar also occurs in a silver vein near Calistoga, Cal. In Idaho float 

 cinnabar has several tisies been found, in some cases with a calcite matrix. 

 A statement repeatedly made in the literature reads as if this ore had been 

 found in place in Idaho, but this is not the case. In Utah, near Marysville, 

 a deposit of the selenide of mercury, tiemannite, was being mined and re- 

 duced early in 1887. So far as I know this is the only case in which this 

 mineral has been found in sufficient quantities to form the basis of commer- 

 cial exploitation. None of the other deposits requires special mention in 



this abstract. 



Discussion of the ore deposits. — The general results of the observations on the 

 various mines are discussed in Chapter XIV. Microscopical examination of 

 the ores shows that cinnabar is usually deposited in immediate contact with 

 quartz, and that, though opal and chalcedony are frequently found very 

 near the particles of cinnabar, there is seldom, if ever, actual contact. More 

 rarely the cinnabar is directly embedded in calcite. The evidence of the 

 microscope also goes to prove that the ore is always deposited in fissures in 

 in dense rocks or in the interstitial spaces of porous sandstones. Macro- 

 scopically the same conclusion had been reached. The assertion often 

 made that cimuxbar has been deposited by substitution for wall rock at 

 Almaden in Spain is certainly incorrect, and, in my opinion, no such case has 

 been adequately proved to exist. The only substance, excepting metallic 

 sulphides, which cinnabar is known to replace is organic matter, and this 

 seems to Ije verv exceittional 



