1064 
MANGANESE DEPOSITS OF INDIA : DESCRIPTIVE. [ PaRT IV : 
cases free from garnets and in others containing an abundance of the 
usual orange-red manganese-garnet (spandite). On breaking up this 
rockit was found to pass inside into an exceedingly tough rock composed 
of plates of a dark greenish to greyish black mineral, which, under the 
microscope, is seen to be a pyroxene of yellow-green to brownish green 
colour, practically non-pleochroic, and showing both prismatic and pina- 
coidal cleavages. The extinction angles in sections parallel to the vertical 
axis range up to 45°. There is also a certain amount of a colourless 
pyroxene (? rhodonite). The pyroxene is seen to be altering very 
largely to manganese-ore, which traverses it as a network, extends along 
cleavage cracks, and unites into patches. In some cases the pyroxene 
individuals are as much as an inch across. In sections showing both 
spandite and pyroxene it is seen that the two minerals have crystallized 
at about the same time, the spandite having perhaps started before the 
pyroxene. This spandite-pyioxene-rock rests on a layer, 6 inches 
thick, o'' a coarsely crystalline Hmestone, which is underlain by similar 
rock. The limestone is probably a small xenolith like the much larger 
once to be noticed below, and contains scattered granules of both the 
garnet and pyroxene. Fresh granules of both the pyroxene and garnet 
extracted from the limestone gave decided reactions for manganese. 
At the junction, the calcite of the limestone interlocks with the large 
plates of the pyroxenic rock and a few interstitial plates of calcite also 
occur in the latter. 
Along the wall B at its northern end the rock is very variegated and 
, consists apparently of masses of more or less 
Pyroxene-spandite-rock. '^^ •' 
blackened pyroxene-spandite-rock (probably 
original segregations) in a matrix of Ughter coloured spandite-fels- 
par rock. Near B irregular patches of spandite-rock, altered pyroxene- 
rock, crumbly fragments of white felspathic rock, and rounded pieces 
of pyroxene-spandite-felspar-rock are set in a 
A fissure-rock. ^ 
matrix composed of little grains of kaolinized 
felspar and spandite in a soft or kaolinic clay-coloured basis ; and the 
whole rock is probably to be regarded as a detrital infilling of a fissure, 
opened out in these soft rocks on account of some change in volume 
produced by the chemical changes that have affected the whole of this 
mass of rocks. One of these included masses is composed of pyroxene(?)- 
spandite-rock and is a yard across. 
