64 
MANGANESE DKPOSITS OF INDIA : MINERALOGY. [ PaRT I : 
paper before the Koyal Society of Edinburgh \ in which he gives a 
somewhat fuller account of the mineral and designates it ' braunite' 
after Braun of Gotha. This is followed by a paper hy E. Turner in 
which is given an analysis of the braunite of Elgersburg in Germany^. 
Turner neglects a residue of silica, which he characterizes as a trace and 
determines the manganese protoxide by difference. In this way Turner 
arrives at the conclusion that braunite is a sesquioxide of manganese of 
the formula Mn203, or, as he puts it, ' an anhydrous deutoxide of 
manganese '. Since then only two other analyses have been published 
that show braunite to correspond to this formula. These are of specimens 
from Arkansas by R. N. Brackett and W. A. Noyes 3, and Elba by C. 
Bechi the percentages of silica being 0"18 and 0'75, respectively. As 
the braunite of Elgersburg was later analysed by Rammelsberg 5 and 
found to contain 8" 63 per cent. Si02, it seems as if the only analyses 
of braunite, corresponding to the formula Mn203, on which it does not 
seem possible to cast reasonable doubt are those of the Arkansas and 
Elba specimens. But it is to be noticed that another analysis of 
Arkansas braunite shows 9-97 per cent, of Si02, the analysis being by 
W. Elderhorst Nevertheless, it seems necessary to recognize the 
possible existence in Nature of a mineral with a composition correspond- 
ing to the formula Mn203 ; it must be extremely rare. All other 
observers have obtained a residue of gelatinous silica on dissolving the 
mineral in hydrochloric acid. From its gelatinous condition it seems 
as if this silica must have been present not as an impurity, but as a 
constituent part of the mineral. The subject is well summarized in the 
already-cited paper of Rammelsberg and in Penrose's book on manganese, 
pages L51 to 153. 
Hermann^ , writing before the essential presence of silica in bra-unite 
had been recognized, supposed, in order to account for the fact that 
braunite is not isomorphous with hematite, Fe203, that the composition 
of the non-siliceous braunites is more truly represented by the formula 
IMnO.Mn02, than by Mn203 : this was on the analogy of the view previ 
ously advanced by Berthier ^ that the composition of the proto- 
sesquioxide is best expressed as 2MnO.Mn02. 
1 TravmcHons, XI, p. 132, (1831). 
£ Op cit., p. 107. 
3 Penrose, Ann. Rep. Geol. Surv. Arkansas for 1800, Part I, p. 140. 
4 Am. J. Sn., 2nd Ser., XIV, p. ()2. (18,52). 
r. Poyy Ann.. (^XXIV, p. .517. (180.5). 
<s First Report of a Geological Reconnaissance of the Northern Counties of Arkansas, 
by D. D. Owen, pp. 104, 105, and 100. (1808) (Penrose). 
V Jour. /. pr. Chem., XLIII, p. 50, (1848), (Rose). 
8 Annalea de Chimie et de Physique, XX, p. 186, (1823), (Rose). 
