194 SMITH— PARAGENESIS OF MINERALS. [Octobers, 



Bank), from which the supposed zoisite was separated, is given by 

 Becker in the w^ork cited. This analysis is quoted below in the 

 table of analyses of the metamorphic rocks, and agrees very well 

 with those of the ordinary basic glaucophane schists. 



Garnet. — This is one of the most abundant minerals in the 

 glaucophane rocks of California, but only in those rocks that have 

 been entirely recrystallized. It is usually in the form of rhombic 

 dodekahedrons, the only form observed, but in the pargasite eclog-' 

 ites of Calaveras Valley the garnet is in anhedrons. It seems to be 

 equally at home in the eclogites, glaucophane schists, and acid 

 gneisses, so that the acidity and the basicity of the rocks have had 

 no influence on its formation, which has been determined entirely 

 by the intensity of the metamorphism. The crystals vary from 

 extremely minute microscopic forms to those 15 mm. in diameter, 

 the largest having been observed in the pargasite eclogite of Hilton 

 Gulch on Oak Ridge, Calaveras Valley. It often occurs in large 

 masses several inches long, but these are really aggregates of small 

 crystals. The crystals in the eclogites are usually surrounded by a 

 kelyphite ring, or reaction zone, of white mica, and chlorite is often 

 formed in this same zone. Occasionally the garnet is entirely re- 

 placed by chlorite. 



The garnet is, apparently, one of the last minerals to be formed, 

 for, although it usually shows well-developed crystal faces, it con- 

 tains inclusions of most of the other minerals. It is pale red, and 

 appears to be of the same character in all of the glaucophane series, 

 but as yet little chemical study has been made of the various occur- 

 rences. The only analysis of the garnet is that of the crystals in a 

 diopside eclogite from Coyote Creek, about six miles north of San 

 Martin, Santa Clara County, made by Mr. W. O. Clark, assistant in 

 geology at Stanford University. 



Analysis of Garnet from Eclogite on Coyote Creek. 



Per Cent. 



SiO^ 38.69 



A1203 I9I0 



FeO 26.81 



MgO 507 



CaO 10-64 



Total 100.31 



