ECLOGITES IN CALIFORNIA 



351 



extinction angle as high as 15° for the angle of C on c\ Small 

 quantities of feldspar and quartz appear in some of the slides. 



The relations of the glaucophane and the chlorite are interesting, 

 as seen in Fig. 3, where the two minerals are apparently reacting in 

 some way. Along the hne of contact there is a deep blue border as 

 indicated in the sketch. In Fig. 4, which is from the same slide, the 

 crystal of glaucophane cuts clearly through the chlorite. The latter 

 has evidently been sheared by some stress, and the glaucophane is a 

 later growth. The chlorite crystal has a definite extinction angle of 



Fig. 3. Fig. 4. 



G = glaucophane, C = chlorite, r = sphene, () = quartz, Ow? =omphacite 



15°, which may indicate formation from hornblende, for the chlorite 

 properly has small extinction angles or no definite extinction. 



The dark hornblende eclogite in Calaveras Valley is the only one 

 of its kind yet found in the state. Macroscopically it shows the dark 

 hornblende with fresh cleavage faces, and with garnets plentiful in 

 some specimens and few in others. Before the blowpipe the horn- 

 blende melts easily to a magnetic globule, at the same time coloring 

 the flame yellow. 



In the slide nearly all possible sections of the hornblende are 

 found, as may be seen in the accompanying microphotograph. 

 The garnets lack the clear outlines so noticeable in the San Martin 

 eclogite. Some of the hornblende crystals are bordered with glau- 

 cophane, which appears white in the photograph. The hornblende 



