i9o6.] SMITH— PARAGENESIS OF MINERALS. 193 



of epidote is poor in iron, and is very likely the mineral described by 

 Becker^ as zoisite, with which it is probably identical chemically. 



Zoisite. — This is rare in the glaucophane rocks, being known 

 to occur as an abundant constituent only in the basic schists asso- 

 ciated with the ecologite of Hilton Gulch on Oak Ridge, Santa 

 Clara County, California. Its form and appearance are exactly 

 like the white epidote, with which it is associated, but its double 

 refraction is very weak in all sections, the colors in thin slides not 

 rising above blue-gray of the first order. A section of the white 

 epidote cut normal to an optical axis can not be distinguished from 

 zoisite in parallel light, but in convergent light the optical figure 

 distinguishes the epidote. Below there is quoted from Becker an 

 analysis of a mineral described by him as zoisite, although his 

 description agrees exactly with the white epidote described above. 

 The mineral analyzed was found in a glaucophane schist, of which 

 the constituent minerals were glaucophane, zoisite (epidote?), 

 quartz, muscovite (paragonite?), albite and titanite. 



Analysis of Zoisite (White Epidote?) from Glaucophane Schist. ^ 



Per Cent. 



SiO. 39.80 



AI2O3 22.72 



Fe^Os 4.85 



FeO : 1.49 



MgO 389 



CaO 17.55 



NaoO 4.09 



K2O 0.12 



TiOs trace 



MnO 0.26 



H2O (above 100° C.) 5-25 



Total 100.02 



This pale epidote was described by F. L. Ransome- from an 

 eclogite near Reed's Station on the Tiburon Peninsula, but it is 

 also abundant in most of the eclogites and glaucophane schists of 

 California. 



A complete analysis of the glaucophane schist (No. 98, Sulphur 



' Mon. XIII. U. S. G. S., p. 79- 



•2 G. F. Becker, Mon. XIII., U. S. G. S., p. 79- 



^ Bull. Dcpt. Gcol. Univ. Calif., Vol. I^ No. 10, p. 310. 



