The Koochichinq Granite. — WincheU. 
295 
Micropegmatitic intergrowths with orthoclase, and apparent- 
ly also with andesine-oligoelase appear sparingly. 
7. Epidote is abundant in small grains. Crystal form is 
quite common, occurring usually in the midst ofbiotite. Twin- 
ning is rare and twinning lamelhie more rare still. In one case 
lamellffi are parallel to a short crystal face in a well defined 
crystal, surrounded by biotite and a bit of quartz. The crys- 
tal gives an optic axis, but no good cleavage is visible. In 
another case (Fig. 1) no lamellae are visible. Two cleavages 
are distinctly traceable, and the twinning plane divides the 
angle between them. The crystal form is again very distinct, 
though part of it has apparently been broken off. The section 
Fig. 1. 
-Crystal of epidote : <?, epidote ; a b, twinning plane ; hi, biotito ; 
q, quartz. 
is 7iearly parallel to the optic plane, and shows an indeter- 
minate interference figure. The twinning is along the line 
a b; the two parts extinguish at an angle of about 1°. It 
seems probable that this crystal and others quite similar 
illustrate primary epidote.* 
8. Kaolin occurs quite commonly in all the feldspars, and 
sometimes may be seen closely aggregated. Being the prin- 
cipal decomposition product of the feldspars, it is most 
abundant in the more highly altered areas, where the vein-like 
structure of secondary quartz and heterogeneous occurrences 
of epidote and sphene are found. 
9. Apatite is seen sparingly, usually in needle-like forms, 
sometimes shortened into prisms. These are usually termin- 
ated by pinacoidal planes, otherwise by pyramids. Apatite 
is seldom, if ever, seen without crystal form. Cleavage has 
* C. R. Keyes : 15 Ann. Rep. U. S. Geol. Sur. 1893-94, p. 706-10. 
