Chap. III. J 
BRAUNITE. 
55 
between the two are subject to great variation, ard such ore can grade 
into psilomelane on the one hand and into the njanular aggregate of 
braunite mentioned above on the other hand. In this mixture the braunite 
individual* sometimes become quite large, as much as k to 1 inch across ; 
but even then the development of crystal faces is prevented by the 
cement of psilomelane, or by the braunite crystals either interlocking 
with or pressing against one another. In one case, namely at Lohdongri 
in the Nagpur district, there are spaces between the layers of ore in 
which the braunite has had the opportunity of developing crystal faces 
(for an account of the exact mode of occurrence see page 917) ; whilst at 
Kajlidongri also, crystals with well developed faces have been obtained 
by Mr. H. J. Winch, presumably from some cavity in the ore ; a single 
specimen was also obtained by the late Mr. A. M. Gow Smith at Kodegaon 
in the Nagpur district. The best locality for crystals is, however, Kach- 
arwahi, where they are to be found in abundance in an albite-rock, fre- 
quently containing blanfordit3 and sometimes quartz, and which as men- 
tioned above is intrusive in the ore-body. One individual showing 
crystal faces was also noticed amongst the ores from Sitapar. The total 
number of specimens from these five localities is considerable, as also 
is the number of faces represented. 
I have not yet been able to carry out a detailed crystallographic 
investigation of all the forms represented, so that 
chS^MtersTvakie'' of I do not propose to give here details of the angular 
the fundamental measurements made up to date. The angle pp' 
'^^^ ' between the faces of the unit pyramid was measured 
on a considerable nimiber of crystals. For this purpose the crystals 
from Kajhdongri were foimd to be the best fitted, since they give the 
brightest reflections. The mean of the value for this angle determined 
over 12 edges measured on 6 crystals was fovmd to be 70^ 22', the range 
in angles being from 70° 17' to 70° 27^'. In the majority of the Kachar- 
wahi specimens the edges are rounded, with a corresponding corrosion 
of the faces, so that good reflections are difficult to obtain. Hence of a 
number of measurements made only 5 were considered to be worth taking 
into account. These were made on five edges distributed over four 
crystals. The values ranged from 70° 13J' to 70° 25i', the mean being 
70° 18|'. Of the Lohdongri braunite only two suitable Specimens were 
available. From these only one measurement was of any value, being 
79° 25'. The Kodegaon and Sitapar specimens were not suitable for 
goniometric measurement. The mean of all the values given above is 
