ECLOGITES IN CALIFORNIA 347 



tine. The eclogite from the Tyrol Alps recently described by Hezner' 

 is composed primarily of clear red garnets, commonly in rounded 

 grains, in a groundmass of emerald-green omphacite. The garnets 

 vary from fine grains up to the size of peas, but the crystal form is 

 seldom distinct. Hezner considers that this eclogite is chemically a 

 gabbro or a variation of the same magma that furnished the gabbro. 

 Eclogite, he thinks, is formed in the greatest depths and in the higher 

 zones amphibolite — the garnet and the omphacite being amphib- 

 olized. 



The foregoing brief extracts will give some idea of the eclogites of 

 Europe and of their probable derivation. , 



CALIFORNIA ECLOGITES. 



Probably the most typical eclogite in California is that found in 

 the bed of Coyote Creek, about eighteen miles southeast of San Jose 

 and some six miles east of north from San Martin. The outcrop of 

 massive rock is exposed for about twenty feet in the edge of the 

 stream. Apparently it breaks through the shale and jasper exposed 

 at the foot of the hill only a few feet away, but the gravel of the creek 

 entirely covers the contact. On the opposite side of the stream, and 

 within a hundred yards, is a large mass of serpentine, which, how- 

 ever, is not in contact with the eclogite. The most characteristic 

 facies of the outcrop is that which shows a grass-green groundmass, 

 thickly studded with dark red garnets several millimeters in diameter 

 and showing distinctly the rhombic dodecahedron form. The faces 

 of the garnet are fresh and shining, with clear-cut edges. The 

 reproduction of the photograph in Fig. i shows the structure of the 

 rock, but the striking effect of the red garnets in the light green 

 groundmass is unfortunately lost. 



Seams and segregations of glaucophane, sometimes bearing gar- 

 nets, occur in the exposure. Prominent veins of a fine-grained red- 

 dish mineral were taken in the field for inclusions of the nearby 

 jasper, but its fusibility, and its isotropic character under the micro- 

 scope, proved it to be a compact variety of garnet. Segregations of 

 actinohte cr}^stals are common, and chlorite frequently occurs. 

 Some particles of chalcopyrite are seen in the rock, and a few parti- 



I Op. ci . 



