ASSOCIATED MINERALS. 389 



crystals occurs in the New Alinaden, tliougli at some distance from ore, in 

 a geode, aeco:n[)anied by bitumen. Specularite is found in hard crusts witli 

 pyrite and cinnabar in the Rinconada and limonite is naturally common 

 near eroppings. I\Ielanterite often forms in the drifts of the mines. Copi- 

 apite occurs both at Redington and at Sulphur Baid<, as was proved both 

 by quantitative analysis and by crystallographic properties. Among the 

 efflorescences in the mines are epsomite from the Redington mine, of which 

 a quantitative analysis was made, anmionia-alum from Sulphur Bank, and 

 borates from the same locality. Pyrolusite is found at the San Carlos and 

 the alta of the New Almaden contains maugane.^o. .Morenosite coats one 

 specimen of millerite, and nickel .silicates are found at the St. John's and at 

 the Phoenix, but no nickel carbonate has been observed. Stibnite occurred 

 with cinnabar at the Manhattan, the Manzanita, and at the Stayton mines. 

 The red sulphide of antimony, for which I have suggested the name meta- 

 stibnite, and arsenic sulphides are abundant in the deposits of Steaml)oat 

 Springs. Chromite is abundant in the serpentine of the Coast Ranges, and 

 hence occurs also near cinnabar, though probably formed long before the ore. 

 In the New Almaden some of the gangue is stained green with chromium sili- 

 cates. The green stains were tested chemically, under the microscope they 

 appear as greenish, cryptocrystalline grains. Two new hydrated chromium 

 sulphates were found in the Redington mine at the point where solfataric 

 gases issue, and they are douljtless the result of the action of these gases on 

 chromite in the serpentinoid rocks. It is proposed to call the more highly 

 hydrated compound redingtonite and that with le.ss water knoxvillite. It i.s 

 needless to point out that a consideralile number of the minerals eivumerated 

 above are products of decomposition processes which have taken place since 

 the original deposition of the ore and gangue. 



Microscopical character.— Many tlun sectious of the ore from different mines 

 have been cut, but under the microscope they give results so uniform that 

 the information thus obtained can be very briefly stated. The cinnabar is 

 transparent only when the section is unusually thin. It is ordinarily only 

 faintly translucent, transmitting dark-red rays, and is much better observed 

 by reflected than transmitted light. As a rule the cinnaba.- seen in slides 

 forms aggregates with oiily occasional crystalline outlines, which are usually 



