108 
MANGANESE DEPOSITS OF INDIA : MINERALOGY. [ PaRT I: 
bloom has been removed, being dull before this is done. The streak of 
this variety is deep brownish black in colour ; its specific gravity is 4*41 , 
the mineral, in spite of its close texture being porous, and thus requiring 
some 3 days soaking before its weight in water becomes constant. The 
fracture is beautifully conchoidal. ' 
J. 917.—Tekrasai. 
This specimen was obtained in situ from a different pit to the two 
preceding. It is also of extremely fine grain, exhibiting beautiful con- 
choidal structure, the colour being a deep blue-grey, whilst in the sun the 
fracture surface shows iridescent reflections. The streak is brownish 
black in colour, the hardness about 5, and the specific gravity 4'38, the 
specimen being non-porous (see Plate 6, fig. 1), 
Scattered throughout the descriptive portion of this Memoir will be 
Calculation of ^'^^^^ Several complete analyses of hand-specimens 
analyses of braunite- of manganese- ores composed of mixtures of braunite 
psilomelane ores. psilomelane. It is possible to make use of these 
analyses for the extraction of further analyses of psilomelane. Before 
giving a list of such analyses I -will give an example of the way in which 
such an analysis can be re-calculated into terms of its mineral composition. 
A good example to take will be the analysis given on page 656 of specimen 
No. A. 607 from Sivarajpur in the Panch Mahals district of the Bombay 
Presidency. The specific gravity of this specimen is 4'25 and inspection 
of it indicates that it consists of numerous tiny grains of braunite in 
a matrix of psilomelane. In calculating the mineral composition the 
P2O5 is first taken out as apatite in the following way, no allowance 
being made for the requisite chlorine or fluorine (these are stated to be 
absent ; but the quantity required for the apatite is so small that it 
would probably be overlooked in the course of analysis) : — 
0-366P2O5 require 0-368 X 1 •312=0-48 CaO, leaving 1-32 - 0-48=0- 84 CaO, and 
yielding 0-846 of apatite. 
The combined silica is next made use of to form braunite, the formula 
of this mineral being assimied to be 3Mn203.MnSi03, since this formula 
is usually found to agree with the analyses very well. 
For braunite 4 '20 Si02 require 
78 '29 
4-20X -—32 -95 Mn203 
9-98 
11-73 
and 4 -20 X =4 "94 MnO- 
9-98 
