Chap. XL. ] 
VrzAGAPATAM : PERAPf. 
1079 
usually predominating, and the rock having a dark greenish black colour 
Under the microscope the pyroxene is seen to be composed partly of a 
colourless variety, possibly rhodonite, and partly of the yellow-brown 
variety found at Kodur. 
This rock is usually more or less altered to manganese-ore. 
In some of the pits, especially in the southern onas, chert is extreme- 
ly abundant, being erey, brown, or black, in 
Chert and flint. ' & & J' ' » 
colour. In the latter case it looks exactly lika 
flint, having also the white outer coating characteristic of that variety 
of silica. Cavernous reticulated psilomelane, with the cavities filled 
with yellow ochre, is usually associated with this chert. 
The rocks on either side of the ore-belt here are probably, as at 
Kodur, scapolitic gneisses ; for two outcrops of 
this rock were noticed, one 200 — 300 yards 
east of the line of pits, and one to the west of the north end of the line 
of pits. 
The character of the ores can be best judged from the constitution 
of sample A.31, taken from some 185 tons of 
thfor*eJ^ ^""^ '^""""^^ stacked ore quarried from the northern group 
of pits. The ore was mostly fairly compact 
psilomelane, a large proportion of the pieces containing small scattered 
crystals of manganese-garnet, while some pieces showed kaolinic specks. 
The analysis carried out by Messrs. J. and H. S. Pattinson showed 
the following : — 
Sample No. 
Scapolitic gneisses. 
4. 31. 
Manganese peroxide 
Manganese protoxide 
Ferric oxide 
Baryta 
Silica (combined). 
Silica (free) 
Phosphoric oxide 
Arsenic oxide 
Water (combined) 
Moisture at 100°C. 
This is equivalent to : — 
Manganese . 
Iron . 
Silica (total) 
Phosphorus 
58-51 
4 04 
18-82 
1-81 
3-50 
0-10 
0-475 
0- 030 
5-20 
1- 00 
40-10 
13-20 
3-60 
0-207 
