70 Washington and Wright — Feldspar from Linosa. 



not a purely sodic raonoclinic feldspar, but an orthoclase in 

 which sodium partially replaces potassium. Also if, as is prob- 

 able, the presence of this Na 2 Al 2 Si 2 8 molecule is verified in 

 other feldspars, the use of the term soda anorthite will be apt 

 to lead to awkwardness and ambiguity. The compound name, 

 furthermore, does not lend itself to the formation of an appro- 

 priate symbol, as Ab, An, and Or, for use in feldspar formulas ; 

 and finally the new triclinic feldspar, which has been actually 

 formed in a pure state, and which we have shown to be capa- 

 ble of existence in nature in mixed crystals, is of such practical 

 and theoretical importance as to deserve a special and distinc- 

 tive designation. For these reasons we propose to substitute 

 for the earlier and essentially descriptive term soda anorthite, 

 applied to the triclinic form of Na 2 Al 2 Si 2 8 , f ne name Carne- 

 gieite (sjnnbol Cg), in honor of the founder of the Institution 

 under whose auspices the mineral was collected and the present 

 investigations were undertaken. 



Locust, New Jersey, and 



Geophysical Laboratory of the 



Carnegie Institution of Washington, D. C, October, 1909. 



