Chap. VII. ] 
ALURGITE. 
197 
SitapcUhur : — The dark brown mica associated with the crimson mica 
mention'^d on page 198 is uniaxial and has the following pleochroism : — 
a = pale straw, 
b and C = rich orange-browa. 
In thick sections there is seen to be a difference between the b and c 
axis colours. They may then be described as : — 
b =: orange-red, 
C = mahogany-brown. 
Flakes of this mineral give a distinct reaction for manganese on 
fusion with, the usual reagents. 
Junawdni : — The mica, which occurs along the cleavage planes of 
the manganhedenbergite noticed on page 131, is bronze to copper- 
coloured and under the microscope shows the following pleochroism : — 
".I == mahogany-red to brownish pink, 
b and c — warm light brown, often with an orange tinge. 
The absorption is c slightly greater than b. The optic axial angle is 
large. 
Alurgite'?), 
Under this name we can group provisionally the various crimson 
and pink micas foimd in association with various of the manganese-ore 
deposits of India. In comparison with the micas of some tinge of brown 
or bronze the rose and crimson micas are rare. I have found them at 
four localities only : — 
1. Kajlidongri, Jiiabu i State, Central India. 
2. Sitapithur, Bliandari district, Centr-.l Provinces. 
3. Glicgara, Xagpur district, Central Provinces. 
4. Kachanvalii, Xagpur district, Central Provinces. 
These micas are found in the following rocks : — 
1 . KdjUdongri : — Here the mica occurs as a deep crimson mineral 
in complex rocks associated with the ^vincllite-bearing rocks, these rocks 
containing winchite, blanfordite, bratmite, apatite, felspar, quartz, 
calcite. The rock is often much altered and the micas consequently seem 
to have to a large extent lost their elasticity and under the microscope 
are seen to be altered and to be made up of alternating laminge showing 
different schemes of pleochroism. The one showing rose ai^d ame- 
thystine tints is the predominant one ; it is not known whether the 
laminae showing orange tints are original or the result of the alteration 
of certain laminae of the crimson mineral. That it is more probably 
original is sho-wn by the fact that a similar mica as far as pleochroism 
goes is also found at Jothvad, in this case apparently in a fresh 
