Chap. XL. ] 
VIZAGAPATAM : KODUR. 
A tlu' soft steps were found to be composed largely of a moderately fine- 
grained rock, which was apparently once a 
{ 4^nvTol'v '''^' ^ ^ ^ ' pyroxene-spandite-felspar-rock (with apatite- 
pyroxene-kodurite), the pyroxene being now 
represented by manganese-oxide pseudomorphs. The walls along Jj 
were also composed largely of similar rocks, which in one place were 
sufKciently fresh to permit of the preparation of a microscope sUde. 
This showed that the pyroxene was entirely converted into manganese 
oxide, and the felspar probably orthoclase ; the pyroxene being 
moulded on to the idiomorjjhic garnet, and the felspar interstitial with 
regard to both. 
Along B is also found a rock composed almost entirely of spandite. 
The rock is a friable granular rock of medium 
titl'rptarroW'"' grain, and dark chocolate-brown colour, and 
sometimes shows little patches of the lavender 
manganapatite to be noticed below. The garnet (spandite) is deep 
orange-red to blood-red where transparent ; and the microscope 
shows, scattered through the rock, a small amount of apatite which 
is allotriomorphic with regard lo the garnet. Along the wall A 
B there is a large quantity of this spandite-rock extending for 
20 paces along the path. The rock contains thin yellowish clayey 
bands. The garnets are often elongated so that the rock shows 
a sort of parallel structure, the long axes of which dip to W. S. W., 
and are hence roughly at right angles to the dip of the rocks (to E. 
N. E.). 
In this rock there is a veinlet, varying from a fraction of an inch to 
4 inches thick and traceable for 4 feet horizon- 
Mangau-nuor-apatitc. i , i • r 
tally, of a lavender coloured variety of mangan- 
fluor-apatite. It is possible that this is a segregation veinlet formed 
during the cooling of the magma from which the spandite rock crystal- 
lized out. 
Another rock found along B is a black altered rock that looks as if it is 
pseudomorphous in manganese oxide after an 
Pyroxene-rock. ... . ^ 
original coarse-grained pyroxene-rock. That 
this is the case is supported by the fact that on the path leaduig down 
to the water's edge at M there is an exposure of a similar rock, m some 
