;56 RULIFF S. HOLWAY 



ANALYSES OF EGLOGITES AND RELATED ROCKS. 



:SiO» 



AI..63 



Fe:.0, 



FeO 



MgO 



CaO 



Na..O 



K..O 



H^O +110°. .. / 

 H.,0 — iio°... i 



CO., 



TiO'o 



MnO. 



Total. 



46.88 



19. 16 

 10.63 



9.48 



99.67 



41 .20 



15.40 

 2.49 

 4.67 



15.51 



12 .26 

 3.44 

 2.49 



1-31 



I. San Martin eclogite, Analysis by C. B. Allen (kindness of Dr. J. P. Smith). 



2 and 3. Tyrol eclogites. L. Hezner. 



4, 5, and 6. Bavarian eclogites quoted, by Newlands. 



7. Glaucophane (eclogite ?) from Oregon. Washington. 



8. Gabbro. Oak Hill, San Jose. Analysis furnished Dr. J. C. Branner by U. S. 

 ■Geological Survey. 



Q. Pargasite, steel-blue to black. Hintze. 



The opinions of Diller, Bonney, and Traube as to the igneous 

 origin of certain eclogites have already been quoted. Harker"^ gives 

 a brief description of eclogites, and quotes Fouque and Levy as to a 

 French hornblende eclogite that is "a local modification of a diorite." 



In connection with the igneous origin of eclogites, the writer tried 

 the experiment of fusing several specimens in a coke assay furnac:. 

 The crucibles were kept at the highest temperature of the furnace 

 for about three hours, and then the drafts were closed and the whole 

 allowed to cool slowly overnight. The eclogites fused easily to homo- 

 geneous lava like obsidian. Under the microscope this showed a 

 practically uniform isotropic character. With a high power points 

 showing double refraction were found scattered through the slide, but 

 no detail could be made out. 



A list of the constituent minerals found in California eclogites, 

 and a brief mention of their properties as they are found in these rocks, 

 will unify the preceding descriptions. 



First among the' essential minerals is garnet. The color is usually 

 a dark red in the hand specimen. In size the garnets vary from 2 to 

 c-mm^ for the well- developed dodecahedrons of the San Martin eclogite, 



I Petrology for Students, 1887, p. 329. 



