AMESJTE AND CORVNDOPHILITESHANNON. 



377 



masses of chromite. The specimen, which was collected by Mr. 

 J. S. Diller, is from the mine of the Placer Chrome Company, 6 miles 

 south of Newcastle, Eldorado County, California. 



The coating of the lavender-colored chlorite is pure and is composed 

 of microscopic crystals loosely aggregated, so that the masses are- 

 reduced to powder in an agate mortar by gentle pressure of the pestle. 

 Such powder when examined optically was found to be homogeneous, 

 and free from included impurities. Upon analysis the following^ 

 results were obtained: 



Analyses of chromiferous chlorite from California. 



1 1 2 Average 



percent, percent, percent. 



SiHca (SiOa) 29. 48 , 29. 24 



Alumina (AI2O3) 



Chromic oxide (CrjOj) 



Magnesia (MgO) 



Lime (CaO) 



Ferrous oxide (FeO) . 

 Water (H2O) 



Total. 



18.81 

 1.80 



35.82 

 1.94 

 1.6G 



11.34 



1.26 



35.52 



2.46 



1.64 



99.60 



29.36 



18.81 

 1.53 



35.67 

 2.20 

 1.65 



11.34 



100. 56 



Column 3 of the above yields ratios as given in the following table: 

 Ratios of chromium-hearing chlorite from California. 



The formula derived from the analysis may then be compared with 

 the commonly accepted formula for clinochlore as follows: 



Despite the deficiency in silica and water shown by the above ratios, 

 the analysis is similar to many which have previously been referred to 

 the kammererite variety of clinochlore. 



Under the microscope the powder is seen to be made up of well- 

 defined hexagonal scales or prismatic aggregates of scales which appear 

 colorless in ordinary light. Basal scales are dark in all positions 

 between crossed nicols, so that the mineral is probably, like most 

 chlorites, biaxial with the axial angle approaching zero, acute bi- 



