VOLUME XXIxX NUMBER 3 
THE 
pew KNAL OF GEOLOGY 
VA EVAN OZ Ts 
THE MINERALOGRAPHY OF THE FELDSPARS 
PARE I 
HAROLD L. ALLING 
Rochester, New York 
Introduction 
(Crystalline) Solid Solutions 
Isomorphism and Solid Solutions 
The Feldspar Components 
The Potassium Component 
Orthoclase 
Microcline 
Dimorphism of the Potassium Component 
The Sodium Component 
Albite 
Barbierite 
The Calcium Component 
Anorthite 
The Barium Component 
Celsian 
 Carnegieite 
Two-Component Systems 
The Soda-Lime Feldspars—Plagioclase Series 
The properties of the Soda-lime Feldspars 
Classification of the Plagioclase Series 
The Potash-Soda Feldspars—The Perthite Series 
‘Undercooling 
Specific Gravities of the Potash-Soda Feldspars 
The Optical Properties of the Potash-Soda Feldspars 
Classification of the Potash-Soda Feldspars 
The Potash-Lime Feldspars—The “‘Oranite”’ Series 
The Barium-Potash Feldspars—Hyalophane Series 
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