GEOLOGY. 181 



spoken of as schists, but although this term is better than shale, 

 it nevertheless conveys an idea of greater metamorphism than has 

 affected the rocks. Here and there, close to granite intrusions, 

 they are converted into phyllites and split along foliation planes 

 with shining micaceous surfaces, but only in rare and extreme 

 cases could they be called mica-schists. They have as a rule no 

 cleavage and so are hardly slates, while they are too hard and too 

 obscurely stratified to be called shales, though shales and mudstones 

 they certainly were originally. The term argillite is probably the 

 most suitable. 



For the greater part they are hard and fine-grained rocks of a 

 blue-grey to black colour when fresh, with obscure bedding and 

 with only an incipient cleavage. Near contacts small crystals of 

 pyrites are common in them. Jointing is very close, splintery and 

 irregular and where the rocks are slightly affected by weathering 

 without being decomposed into lithomarge, they break up easily 

 into small angular fragments. In stream-sections, where expanse* 

 of fresh rock are seen, stratification can at times be made out by 

 differences of colour and texture, and in some cases true slaty 

 cleavage has been produced. 



In the strip of Merguis forming the narrow coastal plain in the 

 south of the district, between Mindat and Pe, metamorphism has 

 gone further than is usual, doubtless owing to the numerous large 

 and small intrusions of granite and pegmatite which invade the rock, 

 and they are largely phyllites and in places even mica-schists, with 

 white pyroxene and garnet produced near the granite contacts. 



The most frequent contact effect is the production of a compact 

 and very tough quartzite of a paler colour than the original argillite 

 probably from the fusion and recrystallisation of the silica of the 

 argillite, with also perhaps the addition of some silica derived from 

 the granite during its consolidation. This often extends for yards 

 from the granite and, being a very resistant rock, is a common 

 site for waterfalls on the streams as they descend from the higher 

 lands occupied by granite io the normal softer Merguis below. 

 Sometimes this siliceous rock is banded in layers of slightly varying 

 composition, the more resistant of which stand out in relief on 

 weathering. 



Several zones of carbonaceous argillites have been noted, as 

 for instance that which is exposed in cuttings on the main Siam 

 road about 11£ miles from Tavoy. It carries small crystal of 



