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MR. 0. BARRINGTON BROWN AND PROFESSOR J. W. .TUDD 
5. Scapolite-gneiss. 
6 ,, granulite. 
7. Pyroxenites. 
8. Amphibolites. 
9. Lapis-lazuli (Lazurite-scapolite-cliopsicle-epidote rock). 
D. Crystalline limestones intercalated in the gneisses, and usually associated with 
the augite- and scapolite-rocks. 
Cipollinos. 
Calciphyres. 
E. In addition to the rocks in situ, we have the interesting gravels and earthy 
rocks formed by the atmospheric disintegration of all the other rocks. 
1. Gneiss, Granulite, and Schist, 
These rocks which constitute the great mass of the Burma area now under con¬ 
sideration are closely related to one another, the dominant rock is a biotite-gneiss, 
which passes into the other two types, granulitic and schistose, by the most insensible 
gradations. The minerals of which these rocks are constituted are as follows :— 
1. Quartz .—This mineral, which is usually abundant, is often darkened, as seen in 
thin sections, by the very numerous bands of inclusions, containing liquids with 
moving bubbles, that traverse the grains in all directions Under polarized light, 
too, the quartz grains often show undulatory extinction and other indications of 
having been subjected to strain. With the quartz exhibiting these phenomena we, 
however, find grains—usually of smaller size—which are perfectly clear and are 
probably of later date than the great mass of the quartz-grains in the rock. 
Felspar .—While both orthoclastie and plagioclastic felspars are present in all these 
rocks, the relative proportions of the two varieties varies greatly in different 
specimens. In the great majority of cases the felspars are somewhat cloudy, showing 
distinct signs of chemical alteration (kaolinization). The phenomenon that especially 
characterises the felspars of these rocks, however, is that known to the French petro- 
graphers as the presence of “ quartz of corrosion.” The grains of felspar are riddled 
in all directions by irregular, and often ramifying, veins of a mineral of higher 
refractive index than the felspar itself. Sometimes these inclusions show no trace of 
relationship in their position to the planes of symmetry in the crystal of felspar; but, 
in other cases, they clearly conform to definite directions within the crystal in which 
they are developed, and thus resemble planes of schillerization.” The crystals with 
those parallel inclusions often show very beautifully the sheen of murchisonite and 
moonstone. The nature and origin of some of these changes will be discussed in 
the chapter on Mineralogy. 
Biotite .— The mica, which is approximately uniaxial, is black by reflected light and 
brown in thin sections by transmitted light. It occurs in irregular scales which, in 
