xxxiv 
MANGANESE DEPOSITS OF INDIA. 
[CHAPTER XYIL] 
The Gondite Bevies— concluded. 
In a discussion of the chemical composition of the series it is shown 
that gondite and rhodonite-quartz-rock would have the compositions 
shown below, according as the constituent minerals were present in 
equal proportions by weight or by volume : — 
(SPESSAEiniiQu'^TZ-ROCK.) ! BH01,0NIIJi.QI7ABIZ-E0CK. 
I 
Equal parts 
by weight. 
Equal parte 
by volume. 
Equal parts 
by weight. 
Equal parts 
by volume. 
MnO . . , . • 
21 46 
26-25 
27-02 
31-25 
ALiOj t • • • • 
10-29 
12-57 
SiOo ..... 
68-25 
6118 
72-98 
68-75 
An actual analysis of a piece of typical gondite from the Chhind- 
wara district corresponds to the following mineral composition : — 
By weight. By volume. 
Spessartite 57-94 46-30 
Quartz 42-06 53-70 
The spessartite is not, however, of the theoretical composition 
corresponding to the formula 3MnO.Al203.3Si02, but has a part of 
the MnO replaced by FeO, CaO, and MgO. 
The question of the alteration of the rocks of the gondite series 
with formation of manganese-ores is then discussed ; the conclusions 
arrived at as to the origin of the gondite series and the associated 
manganese-ores may be summed up as follows : 
Points that may be considered as fairly certain : — 
1. The rocks of the gondite series are the product of the metamor- 
phism of the less pure manganiferous sediments of Dharwar 
age, the metamorphism of these sediments having taken 
place towards the end of the Dharwar period. 
