200 
MR, C. BARRINGTON BROWN AND PROFESSOR J. W. JUDD 
free from lamellar structure. The extinctions of these lamellse point to their being a 
variety rich in lime, and this conclusion is confirmed by micro-chemical examination 
of fragments. The felspars often betray traces of much alteration, and not 
unfrequently exhibit both opalescence and the rich play of colours so common in 
labradorite. Schillerization is frequently displayed, and the so-called “ quartz of 
corrosion "is very common in them. 
Some of the felspars in these pyroxene gneisses are converted wholly or partially 
into scapolite, and numerous beautiful examples of the manner in which this change 
takes place may be found. As I have shown to be the case at Banile, the conversion 
of the lime-felspar into scapolite (dipyre) appears to be a deep-seated one and to be 
one of the results of the clynamo-metamorphic action to which these rocks have been 
subjected. The scapolite itself often shows the first signs of chemical alteration and 
becomes cloudy in ordinary light, while with the polariscope the colours due to double 
refraction are patchy and variable. 
The pyroxene in these rocks is an augite very variable in colour, as seen by 
transmitted light, and forms crystals up to two centimetres in length. Sometimes it 
is of a rich dark green, at other times of a very pale green, becoming occasionally 
quite colourless. Whenever any colour can be distinguished, a very faint pleochroism 
can also be detected, the colours being a bluer green for the rays traversing the 
crystal parallel to the ft axis, and a yellower green for the rays parallel to I) and f. 
The absorption is so slight that I could not satisfy myself as to the direction in which 
it is greatest. This pyroxene often shows the beginning of alteration, ferruginous 
staining appearing along the cracks of the crystal. Schiller enclosures also appear in 
it parallel to both the orthopinacoid (100) and the basal plane (001). The augite 
also shows the beginning of uralitization, the development of the hornblende being- 
accompanied by a separation of magnetite, which renders the mineral almost opaque. 
Sphene is present in some of these rocks to almost as great an extent as the augite, 
and in this respect the Burma rock strongly resembles the well-known augite-felspar- 
sphene rock of Bamle. The sphene occurs in two forms. In the first place, we have 
the large wedge-shaped crystals from 5 to 10 millims. in length, of a yellowish-brown 
colour with slight but distinct pleochroism :— 
ft, very pale yellow, 
f), greenish-yellow, 
f, reddish-yellow. 
Not unfrequently this brown sphene shows signs of alteration. Along the 
cleavage-cracks, especially on the outside of the crystals, black opaque deposits of 
ilmenite are seen, and this is sometimes accompanied by the formation of the white 
opaque material, so commonly observed when titanoferrite is undergoing decomposition. 
On the other hand, we find a number of smaller grains of the perfectly colourless 
sphene (leucoxene or titanomorphite) which is so frequently found resulting from the 
