C'HAl'. \'. ] THE PYROXENES OF THE VIZAGAPATAM DISTRICT. 
137 
The Pyroxenes of the Vizagapatam District- 
In the foregoing table I have not included the brown pyroxenes of 
the Vizagapatam district, where they 
Brown pyroxene. , , 
are oi mucn more common occurrence 
than in any of the other manganese areas, no doubt on account 
of the occurrence of the rocks I have designated manganese- 
pyroxenites. But with most of these I have done little more than 
determine the fact that they are pyroxenes. Amongst the pyroxenes of 
this district there at least three varieties or species, and perhaps four, 
that are probably manganiferous ; for each of them may be found in every 
stage of blackening and alteration to manganese-ore. One of these is 
rhodonite and will not be considered here, but under the heading of that 
mineral. Of the others the best marked is a rich brown to orange-red 
variety forming by far the larger proportion of the manganese-pyroxen- 
ites of Taduru. This mineral occurs in rounded grains up to J inch 
across, and under the microscope is brown in thick sections and pale 
yelloAvish in thin, the pleochroism being very weak. Measurements of 
the angle c a i vary from 8° to ib°. Prismatic cleavage is often marked. 
The^mineral gives a strong manganese reaction. What is probably the 
same pyroxene occurs at Sandapuram and Perapi. 
The second pyroxene is one that is a deep green as seen with the 
imaided eye, sometimes being even greenish 
Green pyroxene. black. It is found at Taduru in association 
with the pyroxene mentioned above, and also at Kodux, Chintelavalsa, 
and Perapi. Under the microscope the mineral usually exhibits some 
shade of brownish green when in thick sections, whilst in thin sections 
it is pale greenish to colourless. In one of the Kodur specimens the 
extinction angle c ^ c ranges up to 35°, referred to the often very well 
marked prismatic cleavage traces. Sometimes the colour in thin shoes 
is pale yellowish rather than greenish. In one such case the mineral 
was faintly pleochroic, a being colourless, and c pale yellowish. 
Besides these two pyroxenes there seems to be a third, which is not 
„ , green or brown as seen microscopically, 
Brownish green pyioxeue. , , . ^ , . i t i 
but an mtermediate colour, namely dark 
brownish green. This variety is also found at Taduru, in prismatic 
crystals up to 1 inch long. In very thick sections the colour is seen to 
be a pale brownish, but in thinner sections the coloiir seems to be a pale 
greenish. This variety is faintly pleochroic, and exhibits very obUque 
extinction. It is also found at Kantikapilli. 
