250 
MANGANESE DEPOSITS OF INDIA : GEOLOGY, [ PaRT II 
it is possible roughly to divide them into groups, according to what may 
be assumed to be the silica percentage of the particular rocks. The 
classification would be somewhat as follows : — 
Quartz-orthoclas?-rock. i 
Apatite-quartz-orthoclase-rock. > Acid. 
Quartz-kodurite in part. ) 
Quarfz-kodurite in part. | Intermediat . 
Orthoclase-rock. ) 
Kodurite. 
Pyroxene-kodurite. ? Basic. 
- . Biotite-kodurite. ) 
Spandite-rock. A 
Apatite-spandite-rock. / 
Pyroxene -spandite-rock. > Ultra-ba-sic. 
Manganese-pyroxenites. I 
Graphitic manganese-pyroxenites. / 
Many of these rocks grade one into the other as one mineral constituent 
becomes more abimdant and another decreases in quantity. The rocks 
grouped as ultrabasic are non-felspathic, whilst all the others contain 
felspar, which is found to be a potash variety, probably orthoclase, 
wherever it is sufficiently fresh to be tested. Apatite occurs in smaller 
or greater quantities in all the rocks. 
Intimately associated with the kodurite series are various varieties 
of vein-quartz and pegmatite. At Garbham a very 
Pegmr.tite and v-^iti silictous pegmatite clearly cuts the kodurite series ; 
' whilst at Kotakarra II, a quartz- felspar-pegmatite 
just as clearly cuts the kodurite rocks. These rocks may hence be sup- 
posed to be of subsequent age to the kodurite series. In some places, 
however, as at Kodur, small veins, not continuous for any length, are 
seen in the lithomarges. Their small extension may simply be due to 
the breaking up of more extensive veins by the slipping of the masses 
of lithomarge ; but, in any case, one cannot help wondering if this 
quartz and some of the pegmatite be not the most acid varieties of the 
kodurite series The apatite bearing pegmatite of Ramabhadrapuram 
has already been referred to (page 248). 
The minerals so far found in the rocks of this series are : — Quartz, 
felspar, apatite, spandite, three or four manganese- 
kol^itf'riei'"^*^' pyroxenes (one of them rhodonite), biotite, 
graphite, and sphene, the three last-named minerals 
being of rare occurrence, and possibly mangan-magnetite. This is 
