METAMORPHIC ROCKS 309 
lighter bands are composed entirely of Quartz or of Fel- 
spar, or are made up of a mixture of these two minerals. 
This in some specimens can be readily done by testing with 
a knife, the Quartz being harder than the Felspars. Note 
the lenticular nature of the bands, the way in which they 
thin out and disappear, reappearing again on the same or 
on a different plane. In some rocks the foliation is so 
massive that it can be seen only in the field. 
Test for cleavage and notice the tendency to split along 
definite lines, 7.¢., in the direction taken by the bands. 
Test for hardness and determine specific gravity. Com- 
pare and contrast with Granite. 
Though Granite is found in many parts of the South 
Island of New Zealand, typical outcrops of Gneiss do not 
occur. 
MICA-SCHIST. 
The schists are crystalline rocks whose minerals are 
arranged in fine folia or layers. In composition they vary 
considerably, and are named after some characteristic 
mineral they contain; the word Schist being employed as a 
suffix. Thus we have Mica-Schist, Hornblende- 
Schist, Chlorite-Schist. 
Mica-Schist, which is probably the commonest of those 
mentioned, may be taken as a type. It consists of a 
mixture of Quartz and Mica in alternating layers; the 
relative proportions of these minerals often vary in 
different parts of the same rock. 
Note the colour of the specimen, which alters with 
the hue of the Mica from light to dark greenish-grey ; 
its smooth silvery surface, and the thin lenticular wavy 
layers or laminae, of which it is composed. Observe 
whether the laminae lie flat, one on the top of the other, or 
ave thrown into folds—contorted. 
