Chap. VI.] 
MANGANESE-GARNETS. 
165 
group, shows affinities to almandite rather than to andradite. In the 
Chargaon garnet, on the other hand, it will be seen that the R2O3 group 
is composed of about equal parts of AI2O3, FeoOg, and Mn203. In this 
respect it diverges considerably from spessartite. It is, however, very 
far removed from andradite, so that again there is no alternative to call- 
ing it spessartite ; unless one invents a special name for a garnet con- 
forming to the formula 3MnO.Mn203.3Si02; this not bemg one of the 
six type garnets referred to on page 161. If such were done, we could 
say that the Chargaon garnet was intermediate between spessartite and 
this other type. Such a course is undesirable and consequently I have 
also called this garnet spessartite. I have, therefore, relpng on these two 
analyses, used the term spessartite for all the manganese-gamets found 
in the rocks of the gondite series wherever they occur, namely in the 
Central Provonces, in Central India, and in Xarukot ; especially since, as far 
as one can tell from outward appearance, they are all the same in mode 
of occurrence, crystalline habit, and the fact that they r^act strongly 
for manganese. The differences of colour that they exhibit are to be ex- 
plained by the replacement of the manganese by iron and other elements 
to a varying extent and by the replacement of the AI2O3 by varjTUg 
amounts of Fe203 and sometimes Mn203. 
If reference be made to the analysis of a manganese-garnet from 
Boirani in Ganjam, given in the fifth column on 
Ori^ of the term page 168, it wiU be seen that this garnet, which 
° ' outwardly resembles some varieties of spessartite 
from the Central Provinces, is practically a variety of grossularite, - 
3CaO.Al203.3Si02, with a small amount of manganese replacing 
a portion of the Ume in the RO group, and with nearly half the 
AJ2O3 replaced by Fe203. But as the RO group of andradite also 
consists of CaO it is obvious that this garnet can be regarded almost 
equally well as a variety of andradite with a httle over half its Fe203 re- 
placed by AI2O3. This garnet might therefore be equally well desig- 
nated iron-grossularite or aluminium-andradite, not considering for the 
present the small quantity of MnO present. To get over this difficulty, 
the mineral may very well be caUed, on the principle explained above, 
grossular -andradite, or for short grandite. If it be desired to express the 
fact that manganese is also present — this after aU being the most impor- 
tant constituent from the economic point of view, as it is this that 
gives rise to the manganese-ores of Boirani — the garnet can be called 
manganese-grandite. From the point of view of brevity this term has 
of course no advantage over the term manganese-garnet and the term 
