10,8 Wright — Calcium Metasilicate. 



however, may or may not retain their character during the 

 change. 



The param orphic change of psendo-wollastonite to wollas- 

 tonite, which is the more imporant from the geologist's stand- 

 point, could not be observed, since the conditions under which 

 it was effected involved solution and precipitation, and did 

 not occur in the solid state. 



- 



Summary. . . 



The chief results attained by the optical study of the calcium 

 metasilicate preparates were : 



1. Identification of artificial wollastonite, whose properties 

 agree precisely with those of natural wollastonite. 



2. Determination of the pseudo-hexagonal, probably mono- 

 clinic, crystal system of the second form of CaSi0 3 ; in its crys- 

 tals the occurrence of distinct and often repeated twinning 

 lamellae parallel to the basal pinacoid and with an extinction 

 angle a : a = 2°, was considered the decisive factor. 



Geophysical Laboratory, U. S. Geological Survey. 



