Chap. III. ] 
BRA UNITE. 
73 
magnesia, baryta, and oxide of iron, with equivalent amounts of man- 
ganese oxides, and then reducing the whole to 100 in exactly the same 
way as was done above in the case of the Indian braimites. Of the five 
examples given below, all except that by Igelstrom are in papers already 
quoted. 
Elgersburg. 
St. Marce'. 
Jakobsberg.I Langban. 
1 
Arkansas. 
Analyst. 
Rammelsberg. 
Damour. 
Igelstrom.l 
Flink. 
Elderborst. 
MnO 
Mn02 
Si02. 
46-90 
44-38 
8-72 
4763 
44-69 
7-68 

46-80 
44 51 
8-69 
4904 
41-16 
9-80 
45 04 
44-94 
10-02 
10000 
100 00 
100-00 
100-00 
100-00 
Manganese 
Available Oxygen 
64-37 
816 
65-16 
8- 12 
64-37 
8-19 
63-99 
7-28 
63-28 
8-02 
Specific gravity . 
4-75; 4-82« 
4-75 
4-72 
On comparing these figures with those given on page 70 for the 
various formulae to which this mineral may correspond, it is seen that 
the Langban and Arkansas braunites correspond to the formula 
3Mn203.MnSi03, the Elgersburg and Jakobsberg braunites to 7Mn203. 
2MnSi03 . and the St. Marcel specimen to the third formula 4Mn203. 
IVInSiOs. The analysis that shows the greatest deviation from the formula 
to which it is closest is the Langban one ; it is evident that this 
deviation is due to too low a percentage of available oxygen, this altering 
the ratio of the manganese protoxide to peroxide considerably. 
The other published analyses to which reference may be made 
are ones by Cap. von Ewreinhoff^ of St. Marcel braunite, showing 
10*16 per cent. Si02 as the mean of two determinations ; ones by 
Damour, also of St. Marcel mineral, showing 10'24: per cent, of Si02 as 
the mean of three determinations ; and one by Tonsager * of braimite 
from Botnedalen, Telemarken, Norway, in which was found 6-22 per cent, 
of Si02 and 3-62 per cent, of insoluble rock powder. It is noticeable that 
these two add up nearly to 10 per cent. From the siUca percentages it 
seems as if the braimites of these locaUties correspond to the formula 
1 Bulletin de la Soc Mm. de France, VIII, p. 423, (1885). 
2 Haidinger, Trans. Roy. Soc Edin., XI, p. 133. 
3 Pogg. Ann., XLIX, p. 208, (1840). 
4 Op. cit: LXV, p. 281. (1S45). 
