f 
CHAPTER XIII. 
G'EOLOGY— continued. 
The Kodurite Series— concluded. 
Alteration of the series and the formation of manganese- ores — Depth to which the 
ores extend. 
The Alteration of the Kodurite Series and the Formation of the 
Manganese-ores. 
Of the various localities that I visited, the Kodur Mines (Nos. 1 to 5), 
Perapi (No. 7), Garbham (No. 11), Kotakarra (No. 12), Avagudem, 
(No. 14), and Ramabhadrapuram (No. 2*^'), showed the felspathic members 
of the kodurite series, with, at Kodur and Perapi, the manganiferous 
pvroxenites free from felspar. At Tadiuu (No. 21) and Chintelavalsa 
(No. 22), however, not a trace of felspar was to be seen in any of the 
manganese-bearing rocks, which are practically all manganese-pyxoxenites. 
As these manganese-pyroxenitss, except at the outcrops, seem to be 
perfectly fresh, no manganese-ores of any value are to be found at 
these two localities. But at all the other localities named above, 
namely those where the felspathic members exist, all the rocks of the 
kodurite series have been subjected to intense chemical action resulting 
in their partial or complete alteration. This chemical action has been 
so widespread that it is practically impossible to find in any of these 
mines a single piece of any of the rocks of this series that has not had 
at least one of its constituents attacked. The consequence is that, as 
noted in the previous chapter, it is only possible to deduce the original 
composition of the rocks of this series by observing the constituents that 
have escaped alteration in different parts of the workings and so deter- 
mining the particular mineral that each constituent of the altered rocks 
represents. Moreover, it is frequently possible to find the fresh form 
of any given mineral passing into its altered form. 
To follow out the chemical changes that have taken place it is 
necessary to know the chemical composition of each constituent 
mineral of the series. They are as follows : — 
Quartz ..... Si02 ...... 
Potash-felspar 1 .... K2O. AI2O3. ().Si02 
Apatite ,'}ra;5P208.CaF2 
Spauditc2 .3(Ca,I\hi)0.(Al,Fe)203.3Si02 
Rhodonite MnSiOs 
Other mangaiies? pyroxenes . Composition not deterniine l . 
1 Assumed to be orthoclase. 
2 With small quantities of MgO and a very small amount of BaO 
