376 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



These ratios may be compared with the amesite formula as follows: 



6(Mg,Fe) 2 (Al,Fe)203. SSiOa- SHgO. Corundopliilite. 

 6(Mg,Fe) 3 (Al,Fe)203. 3SiO,. 6H2O. Amesite. 



Tschermak interpreted corundophilite as a molecular mixture of 

 amesite and serpentine. In pursuance of this interpretation we may 

 experimentally deduct from the ratios of coliman 2 above amesite 

 equivalent to the total R2O3J thus: 



77RO. 26R2O3. 38Si02. GTHoO or corundophilite, 

 minus 52RO. 26R2O,. 26Si02. 52H2O or amesite (X26), 



leaves 25RO. 



12Si02. I5H2O. 



The constituents remaining after deducting amesite then yield as 

 ratios : 



These ratios, considering the manner in which they were derived, 

 are too close to those of serpentine to serve as evidence contradicting 

 Tschermak's hypothesis. For reasons already stated, this line of 

 speculation w411 not be further pursued at this place. 



Optical examination has served to demonstrate the identity of the 

 material analyzed with those examined optically by Descloizeaux 

 and Cooke. The corundophilite is optically positive ( + ), biaxial 

 with moderately large axial angle (±60°). The bisectrix is in- 

 clined about 10 degrees, so that cleavage plates do not extinguish 

 between crossed nicols and yield unsymmetrical interference figures 

 in convergent light. The indices of refraction as measured by immer- 

 sion are: 



q:=1.600±.003 



/3=1.603±.003 



7=1.610±.003 



a-y= .010 ±.003 



The pleochroism, which is marked, is as follows: 



Q!=deep blue-green. 

 /3=deep blue-green. 

 7=pale brownish green. 



Corundophilite may be readily distinguished optically from amesite 

 then by its large axial angle and the inclination of the bisectrix to the 

 cleavage. 



CHROMIUM-BEARING CHLORITE FROM CALIFORNIA. 



A specimen recently transferred to the United States National 

 Museum by the United States Geological Survey (Cat. 93602) show^s 

 coatings of a minutely scaly material of pale grayish-lavender color 

 associated with fine emerald-green crystals of uvarovite on granular 



