Chap. VI. ] 
GRANDITE. 
181 
The specific gravity of this mineral is considerably lower than that of 
spessartite, lying, as might be expected, between that of spessartite and 
that of andradite. The specific gravity of spessartite is given by Dana 
as 4'0 to 4"3, and that of andradite as 3'8 to 3'9. The one actual 
determination of the specific gravity of spandite is that of the speci- 
men from Garbham of which the analysis is given on page 168. This 
value is 4-02. 
The alteration of this mineral is considered on pages 265 — 6 ; and is 
illustrated by fig. 4 of Plate 8. The figures 1 to 4 of Plate 8 
illustrate the occurrence of this mineral. The minerals with wnich it 
is associated at various localities can be seen from the account ot the 
minerals of the kodurite series given on pages 250 — 3. 
Grandite. 
As explained on page 165, this name has been proposed for those 
garnets intermediate in composition between grossularite and andra- 
dite, so that the typical grandite would have its RO or protoxide 
group composed entirely of CaO, and its R2O3 or sesquioxide group 
of about equal amounts of AI2O3 and Fe203. An analysis of an Indian 
garnet corresponding very closely to this ideal composition is given on 
page 168. It also contains a small amount of MnO, namely 2'68%. 
This amount of one constituent would, as a rule, be insufficient to require 
noticing in the name of a garnet. It so happens, however, that this 
is the most important constituent of this particular garnet, because it 
is from this small amount of manganese that the associated manganese- 
ores have been derived. Hence this mineral can be called manganese- 
qrandite. But I shall refci to it merely as grandite. It is found at 
Boirani in the Ganjam district, in a rock composed, when fresh, of ortho- 
clase- felspar, garnet, and a little apatite, the latter being only visible 
under the microscope. Although I cannot be certain that this rock 
is genetically related to the kodurite series of the Vizagapatam district, 
yet the resemblance to the typical kodurite is close enough to justify 
a provisional inclusion of the Boirani rock in this series. The 
only difference is in the composition of the garnet, the Boirani garnet 
containing only a small quantity of manganese, whilst the Vizagapatam 
garnets are highly manganiferous. The Boirani garnet is cinnamon- 
coloured in the hand- specimens, and is usually about -gV to tV inch in 
diameter. Under the microscope it is yellow in colour. Since much 
attention has not been given to this garnet, there is little to say about 
