CONTENTS. 1 1 



Chapter V. — Minerals — Continued. Page. 

 Section 3. Rock-making minerals — Continued. 

 The silicates — Continued. 



Feldspar group— Continued. 

 Monoclinic or pseudomonoclinic — Continued. 



Orthoclase, microcline, and anorthoclase — Continued. 

 Orthoclase and microcline — Continued. 



Occurrence 253 



Alterations 253 



Anorthoclase 257 



Occurrence 257 



Alterations 258 



Triclinic 259 



Albite, oligoclase, andesine, labradorite, bytownite, and anorthite 259 



Occurrence 259 



Alterations -. 260 



Leucite group 266 



Leucite 266 



Occurrence 266 



Alterations 266 



Pyroxene group 267 



Orthorhombic pyroxenes 267 



Enstatite, bronzite, and hypersthene 267 



Occurrence 268 



Alterations _ _ 268 



Monoclinic pyroxenes 271 



Diopside, sahlite, hedenbergite, augite, acmite, spodumene, wollastonite, 



and pectolite 271 



Occurrence 272 



Alterations of the diopside-augite series 273 



Alterations of pyroxenes other than the diopside-augite series 280 



Amphibole group 281 



Orthorhombic. amphiboles 281 



Anthophyllite and gedrite 281 



Occurrence 281 



Alterations 282 



Monoclinic amphiboles 283 



Tremolite, actinolite 1 , cummingtonite, griinerite, hornblende, glauco- 



phane, riebeckite, and arf vedsonite 283 



Occurrence 283 



Alterations _ 285 



Iolite (cordierite) 291 



Occurrence _ 291 



Alterations _ 291 



Nephelite group _ 292 



Nephelite and cancrinite 292 



