66 
MANGANESE DEPOSITS OF INDIA : MINERAL 
\. ART I : 
J. D. Dana', in order to bring ont the crystallographic relation of 
this mineral to rutile, gives the formula as : — 
2 (2MnO.Mn02) + Mn02.Si02. 
Later, however, E. S. Dana 2 adopts Rammelsberg's formula ; in tho 
meantime Rammelsberg, as the result of the discovery of the different 
behaviour of the Mn203 in manganite, a mineral which is isomorphous 
with the corresponding iron mineral gothite, from that of the Mn203 
in braunite, when the minerals are subjected to the action of con- 
centrated nitric acid, changes his views 3 and admits the probability 
that the Mn203 of braunite is really composed of MnO.Mn02. In this 
case he says that the formula may be — 
Mn") 
MnO + >• 02 
Bauer 4 supposes braunite to be an isomorphous mixture of MnO. 
Mn02 and MnO. Si02, in which a portion of the MnO is replaced by 
BaO. Flinks in a paper on the Langban bravmite gives the formula as 
RO.RO2, and arranges the analysis he has made of the braunite of this 
locality as the simi of manganous manganite, MnMn03, and of metasi- 
licates of Mn, Fe, Ca, and Mg, of the general formula RSiOs.s 
From a discussion of the various analyses given below I propose 
to show that it is probable that FUnk's method is the correct one and 
that braunite is to be regarded as an isomorphous mixture of manganites 
of the general formula RMnOs, and of metasilicates of the general 
formula RSi03. This can be stated more generally as — 
7«RMn03 wRSiOa ; 
1 ' Sy.stera of Mineraioaj', 5th Edit., p. 133, fl868). 
2 Op. cit., 0th Ediu, p. 233, (1892). 
3 Silzungf-berichleder Ic. preuss. Akad. Wiss., 1885, 1, pp. 97-100- 
4 ' Lehibuch der MineiaioKie', pp. 31T, 318, (188fi), (Penrose). 
5 Ah. H. Siorlh. Bihang, XVI, (2), No. 4, p. 9, (1890). 
6 Since this was sent to the press I have been able to oltain copies of M. Al. Gorgeu's 
paper ' Sur I'-s oxydes de manRanese naturels issued in three parts. These three parts 
deal with the followin<i minerals : — 
Part I. Bull, dela Soc fr. Mineralojique, III, pp. 21-31, (1890). Psilomelanes 
and wads. 
Part II. Bull, de la Soc. Chimique de Paris, IX, pp. 49C-602, (1893). Polianites 
and pyrolusites. 
Part III. Ibid., pp. 650-661. Manganites, hausmannites, and braunites. 
As the result of analyses of, and experiments on, braunites from St. Marrcl in Pied- 
mont, and Schwarzenbourg in Prussia, Gorgeu conchides (noticing also the analyses 
of Rammelsberg and Damour) that braunite can perhaps be regarded as representing 
an acid salt with the general formula (Mn, Si)02 110, in which the acid portion is formed 
by a combination, in slightly variable proportions, of silicic and manganous acids, and 
in which the basic portion consists of a number of oxides, amongst which MnO largely 
predominates. Ho finds that this combination is only broken up by heat when the 
temperature exceeds that corresponding to a cherry- red. 
