Chap. XL. ] 
VIZAGAPATAM : KODUR. 
1065 
At F is to be found a crumbly and partly altered rock of fairly fine 
grain, composed of orange-red spandite, very 
rorlTwudtoT'''^ P^^^ greyish apatite and a little white felspar 
giving a potassium flame colouration. The rock 
is partly altered with formation of wad and a pale yellowish clay, 
but was evidently once an apatite-felspar -spandite-rock (kodurite), 
the last-named mineral forming perhaps § of the rock. 
In two different parts of the excavation, isolated masses of crystal- 
line limestone are found that are almost 
limestoue'^'' '"y**"^!'""" certainly of the nature of xenoliths torn up 
from below by the mass of intrusive rocks 
composing the manganese-ore belt of rocks. These limestones may 
once have formed part of the scapolitic gneisses (see page 243), and 
may either have been derived from a variety of those rocks containing 
a greater quantity of calcite than usual, or they may have been 
formed from the typical diopside-garnet scapolite-wollastonite-rock by 
the absorption of materials from the intrusives that carried them up. 
One of these xenoliths is exposed at the surface on ^op of the southern 
bank of the mine (XL on Fig. 82), with rounded surfaces and curved 
hollows, such as are made by a stream on a limestone bed. Some 
^^ry jagged quartzose strings and patches were weathered out from 
the mass. It is 13 paces long in a N. E. direction and 12 paces 
across. The rock is a very coarsely crystalline limestone, contains 
green coccolite, — in some place pale green and in others greenish 
black, — wollastonite, sometimes in porphyritic crystals an inch long, 
sphene, scapolite, and some quartz, and beautiful, pale blue, rounded 
prisms of apatite up to i inch long. 
The limestone shows a certain parallel arrangement of its consti- 
tuent minerals and has a dip of 55° to N. 20^ W. ; resting on it at 
the edge of the excavation is a medium-grained rock composed ui 
microcline, and green pyroxene, with sphene, quartz, and ilmenite. 
The second locality for these xenoliths is at XL (Fig. 82) in the 
separate pit (H) to the north of the west end of the main pit. At the 
time of my visit the quarrying operations were uncovering surface 
debris from two rounded masses of crystalline limestone 2 or 3 yards 
apart. One of these masses contained a patch of woUastonite-rock. 
The limestone contained blue apatite. 
