198 CARNEGIE INSTITUTION 



Open crucibles. — The production of crystals of quartz, 

 orthoclase, albite, as well as those of augite, oli- 

 vine, anorthite, etc. 



2. The crystallization of several heteromorphous minerals 



from cooling mixed solutions of the same. Examples: 

 Anorthite and olivine. 

 L,eucite and diopside. 



(a) The order of crystallization related to the rela- 



tive amounts of the two mixed minerals. 



(b) The rate of crystallization. ) In the same rela- 



(c) The habit of the crystals. j tions. 



3. The crystallization of isomorphous minerals from mixed 



solutions. Such as — 

 The series of albite — anorthite feldspars. 

 The series of pyroxenes. 

 The series of amphiboles. 



(a) The order of crystallization. 



(b) The production of distinct kinds, or of crystals 



of average composition. That is, the pro- 

 duction of zonally different crystals, such as 

 the lime-soda feldspars in many cases, or of a 

 homogeneous crystal of intermediate compo- 

 sition. The relation between these modes of 

 crystallization and the rate of crystallization. 



B. With high pressure in closed vessels. 



1 . The effect of the presence of dissolved gases on the crys- 



tallization of anhydrous crystals from liquid rocks. 



2. The effect of dissolved gases on the crystallization of — 



(a) Hornblende as opposed to pyroxene. 



(b) Biotite as opposed to orthoclase and hypers- 



thene, etc. 



3. The relation between pressure and the chemical character 



of the minerals or salts crystallizing from a mixed 

 solution. 



4. The possible crystallization of hydrous minerals such as 



epidote, analcite, muscovite, from liquid rocks under 

 pressure (to account for " primary " epidote and anal- 

 cite in igneous rocks). 



5. The possible crystallization of calcite and other carbonates 



from liquid rocks. 



