Chap. III. ] 
BRAUNITE. 
63 
According to Dana's ' System of Mineralogy ' braunite shows the 
following characters : — Cleavage : perfect parallel 
Physical characters ^^iq faces of the tetragonal pyramid or octahedron. 
of braimitf. ° i" . i i t~> • i tt 
Fracture mieven to sub-conchoidal. Brittle. H.= 
6-6-5. G = 4*75- 4-82. Lustre submetallic. Colour dark brownish 
black to steel-grey. Streak same. 
In most respects the Indian braunites agree with the above. Thus, 
of the three specimens of braunite of which the analyses are given 
below, two have a specific gravity of 4-79, whilst the third, which con- 
tains a considerable quantity of magnesia and is therefore not typical, 
lies outside the limits given above, having G. =4-70. On crystal faces 
the lustre can perhaps be correctly designated sub-metalUc, but on 
fresh cleavage surfaces it is brilliantly metallic. The colour of the 
Indian braimites is never brownish black as far as I have seen, but 
may be either a pure black or a deep steel-grey. 
A feature of this mineral, which is not, however, mentioned in the 
diagnosis given by Dana, is that the mineral is 
Magnetic characters, •j^^j^j.j^^^y slightly magnetic. The strength of this 
property varies greatly, and is sometimes quite strong. If some of the 
tiny grains composing the braunite-psilomelane mixtures of the 
Central Provinces be detached from the ore they can almost invari- 
ably be picked up by a small hand magnet, or at least made to move 
slightly under its influence. The magnetic properties of the Indian 
braimites might be thought to be due to their contents of iron. This, 
however, does not necessarily follow ; for the specimen (16-815) of 
which the analysis is given on page 68, though not corresponding very 
closely in composition to the theoretical braunite (in fact I have 
separated it as a variety of this mineral), contains only a very small 
quantity of ferric oxide compared with some of the Indian braunites. 
It is. however, just as strongly magnetic. 
The question as to the chemical composition of braunite has been 
the subject of repeated discussion, and it cannot 
Coinposition of ^^^^ ^^lat even now this point has been satis- 
braunite. i t mi • ^ 
factorily settled. The mmeral was first distinguished 
as a separate species by Haidinger in 1826.^ In this paper he calls the 
mineral ' brachytypous manganese-ore ' and notices specimens from both 
Elgersburg in Thuringia and St. Marcel in Piedmont. In 1827 he read a 
1 Edin. Jour. Sci., IV, p. 48 (Dana); translated into German in Pogg. Annattn, 
VTI, p. 234.(1826). 
