Chap. III. 
MANGANlTc 
83 
Manganite 
Manganite is a hydrated oxide of manganese having the formula 
Mn203.H20. It crystaUizes in the orthorhombic system in prismatic 
crystals usually exhibiting several different prism faces ; the termina- 
^ te s ^^^^ usually a basal plane, although this is some- 
times absent, pyramid and dome faces being develop- 
ed instead. The crystals are often many times longer than broad, then 
assuming a needle-like aspect. The colour is stated to be steel-grey 
to iron-black and the lustre sub-metalUc, with the streak reddish brown 
to nearly black. Hardxiess =4. Specific graxaty = 4'2-44. \\Tieu 
pure the miaeral contains 62*50 per cent, of manganese and 10*23 per 
cent, water. 
According to Mallet a specimen of this mineral has been obtained 
from the PoUtical Agent at Gwalior, and hence pre- 
Occurrence. 
sumably from that neighbourhood, i I have shovv-n 
elsewhere that this specimen 2 is probably only pyrolasite, although the 
crystals may be pseudomorphous after manganite. 
In a paper in the Records of the Geological Survey of India, 
Vol. XXXIII, pages 229-232, I have described and figured an example, 
there supposed to be manganite, occurring as a hning to a geode found 
on the outcrop at Raman drug in the Sandur Hills. At the time this 
paper was written this was the only known specimen of this character. 
Since then, however, Mr. Aubert, who obtained that specimen, has pre- 
sented to the Geological Survey several more similar specimens from the 
same locality. The specimen described in the paper exhibits well the long 
needle-Uke habit, showing usually the faces of a prism, sometimes accom- 
panied by other bevelling prisms, with for termination either the basal 
plane or, more rarely, a couple of minute faces that suggest the macro - 
dome. The mineral differs from typical manganite in that it does not 
seem to give off, when heated in a closed tube, a large enough quantify 
of water, probably owing to incipient change to pyrolusite. It is noticed 
that the perfect cleavage of manganite parallel to the brachypinacoid 
b (010) causes it to decrepitate violently when heated in a closed tube, 
the mineral splitting along this direction. The lustre, moreover, is not 
sub-metalUc as stated by Dana, but brilliantly metallic, the colour 
being, moreover, bronze, due perhaps to a superficial tarnish 
1 Mineralogy of India, p. 59,(1887). 
2 Rec. Geol.Sur. Ivd., XXXIII. p. 232.(100()J. 
