62 BULLETIN 149, UNITED STATES NATIONAL MUSEUM 



ination. Only an exceedingly small light portion was obtained. This 

 consisted of grains of feldspar containing numerous inclusions of the 

 silicate of higher index, probably pyroxene for which the feldspar 

 forms a matrix. Practically none of the feldspar grains showed twin- 

 ning and most of them had a refractive index, beta, of about 1.550, 

 varying about 0.002. 



The unused portion of the unattracted powder was likewise screened 

 free from fines and passed through heavy solution. The lightest 

 product separated from this likewise consisted of only a few mixed 

 grains consisting of a feldspar with very abundant rounded inclusions 

 of pyroxene and olivine. The feldspar showed no twinning and is 

 optically positive with 2V medium, beta index from 1.550 to 1.553. 

 The feldspar thus appears to be a fairly sodic plagioclase approaching 

 andesine in composition. Occasional grains of the feldspar-bearing 

 material are heavily pigmented with a black substance which is 

 probably largely carbon. 



The heavier concentrate from the insoluble silicate consists of a 

 few clear grains which exhibit moderately high bi-refringence. A 

 majority of these were aggregate in structure, greatly dusted with 

 inclusions and gave very little optical data. The clearer grains were 

 biaxial and positive with a beta index of about 1.680. No cleavage 

 was observed and only one or two grains showed recognizable poly- 

 synthetic twinning. The optical properties are those of diopside. 



o 



