Chap. VI. ] 
SPANDITE. 
179 
surrounding the separate grains of quartz. The alteration of this 
mineral is discussed on another page (354), and is illustrated by figures 
1 and 2 on Plate 1 2 ; whilst the form of the mineral as viewed under 
the microscope is illustrated by figures 1 to 3 of Plate 1 1 . 
Spandite. 
As already explained (page 163), 'spandite' is a name proposed 
for the varieties of manganese-garnet that are 
Composition. . , , . . ,. , 
intermediate m position, as regards composition, 
between spessartite and andradite. An ideal specimen of spandite 
would contain about equal proportions of manganese and calcium in 
the protoxide group and about equal proportions of iron and alumi- 
nium in the sesquioxide group. Analyses are given on page 168 of two 
specimens of spandite from the Vizagapatam district, and since these are 
considered to be representative of the whole of the manganese-garnets 
occurring in the kodurite series of this district, I propose to designate 
all the manganese-garnets found in this series by this name. At pre- 
sent, moreover, no analyses of manganese-garnets have been made that 
justify the application of this name to manganese-garnets outside this 
district. Consequently the mode of occurrence of this variety of garnet 
will be best understood by reading the account of the kodurite series 
given on pages 243 — 2.55. The characteristic rock in which this mineral 
is found is the one I have designated kodurite. This 
Oecurrence. . ,. i r i .•■ i t 
consists 01 potash-ielspar, apatite, and spandite. 
Often quartz is present as well, the rock then being quartz-kodurite ; 
whilst sometimes the garnet forms practically the whole of the rock, 
which is then known as opandite-rock. The best locality for span- 
dite-rock is Kodur. As explained on page 247, the rocks of this 
series are supposed to be of igneous origin, and as the spandite is con- 
sidered to be an original mineral, this origin must also be ascribed to 
it. Not only is it found in the rocks of the kodurite series, but it is 
frequently present in the ores that have been formed during the chemical 
changes that have affected the rocks of tliis series since their formation, 
with the production of merchantable manganese -ores. In these cases 
it often appears as bright red garnets set in a matrix of manganese-ore, 
usually psilomelane. On Plate 8, fig. 4, is a photo-micrograph of 
such ore. showing the psilomelane growing at the expense of the 
garnet. The best locaUties for such specimens are Garbham and 
Ramabhadrapuram (MamidipilU). The following is a list of the. 
I n2 
