CHAPTER XVII. 
GEOLOGY— continued. 
The Gondite Series— concluded. 
Chemical composition — Alteration of the gondite series — Evidence of alteration — 
Time of alteration — Method of alteration — Depths to which the ores extend — Conclu* 
sions as to the origin of the gondite series and associated manganese -ores. 
Chemical Composition of the Gondite Series. 
As can be judged from the list of rocks given on page 329, the com- 
Composition of position of the rocks of the gondite series is very 
gondite. variable, and I propose to consider here only a few 
of the less complex members. As has been already mentioned, the type 
rock of this series may show every gradation in composition between 
quartz-rock free from spessartite and spessartite-rock free from 
quartz, i.e. between SiOg and 3(Mn,Fe,Mg,Ca)0.(Al,Fe,Mn)203.3Si02, 
assimiing this to be the composition of the manganese-garnet of the 
Central Provinces. In a case in which the garnet had the theoretical 
composition of spessartite the composition of spessartite-rock would 
be as follows : — 
MnO . . . 42-92 
AI2O3 . . .20-58 
SiOz . . . 36-50 
Gondite composed of equal parts of quartz and spessartite, in one case 
by weight and in the other by volume, would have the composition 
shown below : — 
Equal parts by Equal parts by 
weight. volume. 
MnO . . . . 21-46 26-25 
AI2O8 .... 10-29 12-57 
SiOa .... 68-25 61-18 
100-00 100-00 
An actual analysis was made of a piece of typical gondite (16-984) 
from Wagora in the Chhindwara district. This is the rock of which a 
photomicrograph is given on Plate 11, fig. 2. It is a cinnamon-pink or 
pinkish buff rock of fine grain. The specific gravity of the piece 
analysed was found to be 3*42. Under the microscope the rock is seen to 
