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[Vol. LXXIV 



Fig. 4. Gnomonic projection of glaucochroite forms. 



The last value approaches that of tephroite, as shown in the 

 following table, in which all the members of the Olivine group 

 are listed in the order of increasing length of the a-axis: 



The refractive indices of one of the crystals measured were 

 higher than n 1.740, so that the present mineral is probabty inter- 

 mediate in composition between glaucochroite and tephroite. 



WlLLEMITE 



One of the specimens obtained consisted essentially of frank- 

 linite and willemite on which was a cavity containing a number 

 of brilliant, greenish, transparent, highly modified crystals of 

 willemite associated with glaucochroite. A single crystal, ^ x 1 mm. 

 was measured. The general habit of the 'crystals is indicated in 



