Vol. 4] Murgoci. — Classification of the Amphiboles. 



387 



II. 



MATERIALS STUDIED. 



GLAUCOPHANE SCHISTS. 



On the Califoniifm glaucophane schists there is an extensive 

 literature, hut in California, as in other countries, the problems 

 are far from being' solved. I add here some petrographic notes 

 on some of these rocks merely as suggestions for future work, and 

 especially as proofs in support of the theories advanced in the 

 preceding section of this paper. 



The numbers in these notes refer to the collection of slides of 

 Professor J. P. Smith. 



Eclogitc. — Arroyo Hondo, Calaveras Valley. I. (4, 5.) Gar- 

 net in large crystals with inclusions of titanite, rutile, apatite, 

 and karinthine, with patches of glaucophane. Ilmenite with 

 edges of magnetite ; hematite, golden yellow rutile sometimes in- 

 cluded in titanite, epidote ; lawsonite. Karinthine, with inclu- 

 sions of zircon with halos of titanite rutile, etc., shows: C — 

 blue-green, 6 = dark olive-green, a =; yellowish to colorless. 

 Patches and edges of blue-violet glaucophane, max. ext. = -24°. 

 2 V large ; the basal sections show an optic axis. Negative. 



In another slide with much titanite, the karinthine with edges 

 and patches of glaucophane gives a max. ext. -27° with stronger 

 absorption (the colors much darker). 



Another slide shows a karinthine: C = blue green, b = dirty 

 olive-green, a = yellowish green; ext. -28°; 2 V very large;* 

 y — a large; negative; axial plane =(010); a basal section 

 shows an optic axis at the edges of the field of the microscope. 

 Glaucophane shows: C = azure blue to ultramarine blue, b = 

 violet, 8 = bluish to colorless; 2 V large; negative; intergrown 

 with karinthine. 



Greenstone.— Calaveras Valley. I. 8, 8 (No. 10). Titanite, 

 rutile, ilmenite, hematite, epidote, lawsonite (?), karinthine chlo- 

 rite, glaucophane intergrown with karinthine. Karinthine shows : 

 C = bluish green, t) = olive green, a = yellow to colorless; ab- 

 sorption slight ; ext. -20° ; negative ; basal sections show a second 



* Very large is over 60° ; large is 60° — 40° ; small is less than 40°. 



