University of California. 



[Vol. i. 



brilliant, somewhat pearly luster. Before the blowpipe they fuse 

 easily, and answer well to the characters of margarite. A very little 

 water is given off by strongly heating in a matrass. Cleavage 

 flakes show the emergence of a negative acute bisectrix on the 

 basal plane, with a large axial angle. This mineral occurs mainly 

 filling veins in the schist, and inclosing crystals of lawsonite with 

 occasional masses and crystals of pyrite. 



A light-colored epidote is also very abundant in certain portions 

 of the schist, in aggregations of small crystals, forming streaks and 

 bands through the rock in the direction of schistosity. The color 

 varies from pale greenish yellow to almost ash gray. The lens 

 shows that the crystals are columnar in habit, without distinct ter- 

 minations, with the faces finely striated longitudinally, and possess- 

 ing a perfect cleavage in a plane parallel with the axis of elongation. 

 Before the blowpipe, the mineral fuses with intumescence to a dark 

 brown slag, which readily gelatinizes with acids, the solution react- 

 ing for lime, alumina, and ferric oxide. The specific gravity, deter- 

 mined by suspending particles in Klein's solution, is 3.326. 



Cleavage flakes show a biaxial figure, of which one hyperbola 

 only appears in the field. The plane of the optic axes is transverse 

 to the direction of crystallographic elongation, and the optical sign 

 is negative. This corresponds with the usual orientation of the axes 

 in epidote. The dispersion is p<v. Cross sections (clinopinacoidal) 

 of the crystals are generally irregular in outline, but occasionally 

 show the hexagonal contour, and inclined extinction of epidote. 

 Such sections give no interference figure. The cleavage is not so 

 conspicuous in micro-sections as would be expected, and in clino- 

 pinacoidal sections is difficult to detect. Cleavage flakes, and sec- 

 tions which are not too thin, exhibit distinct pleochroism, t pale 

 greenish yellow, I) fainter yellow, and colorless or grayish, the 

 absorption being c>6>0. The index of refraction is high, but the 

 double refraction is not conspicuously strong, the colors between 

 crossed nicols rarely mounting above those of the amphibole min- 

 erals in the same slide. 



The conclusion from the foregoing description is that the min- 

 eral is an epidote poor in iron and closely approaching zoisite in 

 composition, the poverty in iron accounting for the pale color, faint 



