CONTENTS. W 



Chapter V. — Minerals — Continued. Pa s°- 



Section 3. Rock-making minerals — Continued. 

 The oxides— Continued. 

 Quartz— Continued. 



Modifications 218 



Tridymite . 



Alterations . 



Alterations . 



Eutile group. 



220 



Occurrence ^"° 



Modifications 2 ~° 



Opal 221 



Occurrence - 



Modifications 22i 



Chert, chalcedony, etc """ 



Hematite group , -'-" J 



Corundum, hematite, and ilmenite - - 22, 3 



Corundum 2_J ^ 



Occurrence - — J ° 



223 



Hematite 225 



Occurrence "- 



Alterations - "-" 



Ilmenite - "'-' 



Occurrence 22 ' 



Alterations 22 ? 



Spinel group "~° 



Spinel, magnetite, and chromite 228 



Spinel 228 



Occurrence "~° 



228 



Magnetite 229 



Occurrence 22 ° 



Alterations ; 229 



Chromite. 229 



Occurrence 2 - 9 



Alterations - 2 ^0 



230 



Eutile, octahedrite, and brookite 2 30 



Occurrence 2 ^0 



Alterations 2 30 



Diaspore group - - "^1 



Diaspore and limonite 2 31 



Diaspore - - 2 ^ 2 



Occurrence 2 ^ 2 



Alterations 2 ^ 2 



Limonite 2 ^- J 



Occurrence 2 ^2 



Alterations , - 2 ^3 



