I9I0.] COAST RANGES OF CALIFORNIA. 345 



It occurs in white chalk-like masses to which green inclusions of 

 serpentine give a mottled appearance and which readily crumble 

 away under slightest pressure. The ratio of serpentine to hydro- 

 magnesite is approximately as one is to two. An analysis of the 

 purest sample gave results as follows : 



Analysis of Hydromagnesite. 



H. E. Kramm, analyst. 

 SiO^ 9-37 



F^=0^j trace 



ALO3 j 



CaO 2.46 



^IgO 39.25 



CO2 29.45 



H.O 18.74 



99.27 



Crystals of hydromagnesite are found near Cedar Mountain in 

 Alameda County. 



Calcife occurs as veins in the serpentine and is a prominent 

 constituent of the siHcious mass to which serpentine gives rise. It 

 is also found closely associated with the serpentine in what is known 

 as ophicalcite. Specimens of ophicalcite which are a mixture of 

 about one half calcite and one half serpentine were found at the 

 Mirabel Quicksilver Mine in Lake County and at New Almaden in 

 Santa Clara County. 



Dolomite has an occurrence similar to that of calcite. 



Aragonite is found in the neighborhood of Pine Mountain. At 

 the Helen quicksilver mine in Sonoma County it occurs as needle- 

 like crystals and fibrous crusts. 



Epsoniite. This mineral is found lining the shaft and drifts in 

 the Knoxville Mine. Hair like crystals, snow white in color, some- 

 what brittle, with a silky luster often reach a length of a foot or 

 more. 



Melaiiterite is usually found as greenish-white hair-like crystals 

 reaching a length of several inches, lining shafts and drifts in quick- 

 silver mines. In the Knoxville mine it also occurs in stalactitic 

 masses of a pale green color, which seem to melt in their own 

 water of crystalhzation. On exposure to light it becomes dry, as- 

 sumes a yellowish-green color and changes into copiapite. 



