THE SOUTH KUN COMPLEX. 119 



or the |)laiies ut' the prism e<)nil)iiie(l with the niacropiiiacoids. 'I'lic ti-i'- 

 ininal i)hines are not often well ileveloped. The pleoehroism ot'the liorn- 

 blende is very unit'orin; c dark j^-reenisU blue, b dai-k green, a hone^- yel- 

 low. The ab.sorptiou is: b >C!>a; c : C varies from 13° to If)". The horn- 

 blende individuals always include many g-rains of the other minerals 

 present, usually more quartz and feldspai- than of cldorite and biotite. It 

 apparently shows by its inclusions, combined with its idiomorphic forms, 

 that it was the last mineral to crystallize. Its growth within these gneisses 

 may be compared to the growth of crystals of garnet and staundite in 

 staurolitic and garnetiferous mica-schists, which frequently include large 

 quantities of foreign materials. In its develo})ment, if a late mineral, it 

 took within itself such material as it could not force aside. More often in 

 the gneisses the horidilende is in small 1)lades free from inclusions, located 

 between the particles of quartz and feldspar or else penetrating them 



The biotite and chlorite occur in well developed folia, and in small 

 fibers and irregular areas. Each of these minerals is in turn in quite a 

 nnndierofthe exposures the chief constituent aside from the (piartz and 

 teldspar. Each frequently contains numerous smaller particles of what is 

 faken to lie o.xide of iron, which are arranged withiu their parts in the 

 same regular manner. A portion of the chlorite and biotite is certainly 

 secondar\' to feldspar and hornblende. This is ])articularh' ti'ue of the 

 chlorite. However, there is no evidence that their alnindant, well defined 

 blades are sec(mdary. The epidote, so plentifully present at times, is found 

 alike in the feldspar, chlorite, hornblende, and biotite, altliougl; most com- 

 mon in the first two. It occurs in numerous small granules and large 

 irregular areas. A large part of it is certainly derived from feldspar, chlo- 

 rite often lieing an intermediate stage in its formation. It also has forined 

 from hornblende. In some of the rocks the epidote is with quartz the chief 

 constituent and the rock conseqiienth' is an ei)idosite. There is here no 

 evidence of the derivation of the epidote from feldspar, hornblende, and 

 chlorite, but it may be true that the r(K-ks in which tlu' origin of the 

 epidote is plain is an intermediate ])hase in the formation of the epidosite. 

 The other accessories most frequently present in the gneisses are pyrite and 

 iron oxide; tourmaline is rarely found. 



