10 CONTENTS. 



Chapter V. — Minerals — Continued. Page. 

 Section 3. Rock-making minerals — Continued. 

 The oxides — Continued. 



Brucite group , 234 



Brucite and gibbsite 234 



Brucite 235 



Occurrence 235 



Alterations 235 



Gibbsite 235 



Occurrence 235 



Alterations 235 



The carbonates 236 



Calcite group _ 237 



Calcite, dolomite, ankerite, parankerite, magnesite, and siderite 237 



Calcite 237 



Occurrence 237 



Alterations 238 



Dolomite 240 



Occurrence 240 



Alterations 241 



Ankerite and parankerite » 242 



Occurrence 242 



Alterations 242 



Magnesite 243 



Occurrence 243 



Alterations 243 



Siderite 244 



Occurrence 244 



Alterations 244 



Aragonite group 245 



Aragonite 245 



Occurrence 245 



Alterations 245 



The silicates 246 



Glass 246 



Occurrence 247 



Evidence that devitrification takes place 247 



( Scale of devitrification . 247 



Rate of devitrification 248 



Devitrification in the two zones 249 



Minerals produced 251 



Heat and volume relations 251 



Feldspar group 252 



Monoclinic or pseudomonoclinic 253 



Orthoclase, microcline, and anorthoclase 253 



Orthoclase and microcline 253 



