388 University of California Publications. [Geology 



bisectrix and an optic axis. Glancophane variable in pleochroism 

 and absorption from pale colors to very dark ones ; 2 V also va- 

 riable from large to zero ; negative. 



Greenstone (eclogite). — Calaveras Valley. I. 7. Well de- 

 veloped crystals of titanite ; rutile with halos of leucoxene; karin- 

 tliine, clinozoizite (colorless epidote) in large crystals, lawsonite, 

 lotrite (?), quartz, chlorite with biotite and muscovite. Glanco- 

 phane occurs in lamellae with variable pleochroism and absorp- 

 tion, with remains of karinthine faintly colored like the glauco- 

 phane in general. As veins, or mixed with the other minerals in 

 the rock, we find a yellowish mineral here and there with some 

 greenish pigment ; it occurs as lamellae and fibers with cleavage 

 sometimes very well pronounced, often disposed in fans, forming 

 sometimes a radial spherulite. The refractive index is 1.67; the 

 occurrence and properties suggest lotrite. The lamellae with 

 strong birefringence (y — a) extinguish symmetrically ; some 

 other lamellae give wavy extinction, and those with /? — a very 

 small show an angle of extinction of 15°. Belief and birefrin- 

 gence a little higher than in glancophane. Pleochroism: il C 

 — colorless; fa = greenish. The length of the lamellae is parallel 

 to b; axial plane perpendicular to the cleavage; 2 V large down 

 to very small around a positive bisectrix, even uniaxial. Accord- 

 ing to these properties this mineral is very similar to lotrite. from 

 which it differs only slightly in the angle of extinction.* The 

 lotrite ( ?) seems to be in genetic relation with the glancophane 

 and karinthine ; some lamellae of glaucophane and karinthine 

 pass into a mass of lotrite lamellae. The glaucophane, however, 

 at the contact with the vein of lotrite ( ?) shows clearly a trans- 

 formation into crossite. (Fig. 6.) It becomes very intensely 

 colored (blue and violet), almost uniaxial, and the edges and 

 lamellae which project into the interior of the vein have a much 

 stronger pleochroism and absorption, and the optic orientation 

 of crossite: C = dark violet; fa = Prussian blue to indigo; a = 

 gray-violet; ext. -19° ; birefringence very small; 2 V very large; 

 dispersion very great. Karinthine shows an extinction of 19°, 



* For lotrite see : Granat-Vesuvianf els von Paringre by the author in 

 Bulet. Soc. Seiinte., Bucharest 1901. Refer. Groth's Zeitschrift; Neues 

 Jahrbueh, etc., and Eosenbusch. 



