43 
Records of llie Geological Survey of India. 
[vol. VI. 
Mineealogical notes on the Gneiss of South Mirzapur and adjoining country, 
by F. II. Mallet, f. g. s., Geological Survey of India, (No. II.) 
Having last season found the limestone of the Bichi nadi* to he a normal dolomite, I 
Limestones collected specimens from various localities this year, in order to 
ascertain how far this character is general in the limestones of 
the gneissose series. On analysis I obtained the following results:— 
I.—Calcite Limestones. 
A. 
B. 
C. 
Carb. of lime 
... 97-92 
83-12 
85-92 
„ „ magnesia 
... ... 1-47 
7-04 
8-19 
„ „ iron 
•38 
l-28f 
■76 
Insoluble 
■80 
1016 
5-52 
100-57 
101-60 
100-39 
II.- — Dolomite Limestones. 
D. 
E. 
E. 
Carb. of lime 
... 67-28 
64-68 
53-85 
„ „ magnesia 
... 30-24 
34-14 
45-78 
„ „ iron 
•78 
•58 
•34 
Insoluble 
•50 
•76 
1-00J 
98-80 
100-16 
100-97 
A is a very coarsely crystalline white limestone, from south of Bilwada on the road from 
Singrauli to Mirzapur; B a dark grey fine-grained crystalline rock, from east of Karami, 
(sheet 18, Kiwa Survey); C is a white and greenish-white, rather fine-grained crystalline 
rock, which occurs in subordinate beds tlmough the dolomite E. It weathers with a smoother 
surface, and is tougher on account of its more compact texture. D is a rather finely crys¬ 
talline, or saccharine, white dolomite, from the banks of the Bekr, south-west of Ekpai; its 
composition corresponds nearly to the formula 2C'aO, CO, 2 + MgO, CO.. E is a white 
rather coarsely crystalline rock from north of Pararwa, ha ving the composition 3CaO, C0 2 
+2MgO, (.'0. 2 ; while F is the white crystalline normal dolomite (CaO, C0 2 + MgO, C0 2 ) 
of the Bichi nadi already referred to. 
It will thus be seen that the limestones vary from pure carbonate of lime to pure dolo¬ 
mite. In some cases, of which C and E are examples, the two rocks are interstratified. 
The above dolomitio limestones are all associated with more or less serpentine; and I think 
it may be assumed that where the latter mineral is present in any quantity, the limestone 
is magnesian. In the only case I have hitherto observed in which serpentine is actually 
interbauded with the limestone the latter is true dolomite. 
In the two patches of gneiss cast of Koclkat (sheet 18) occurring as inliers in the 
Takhirs, limestone is very abundantly met with, the same beds 
being probably repeated by folding, with a general strike of about 
west 30° north. It is a white crystalline rock, varying from a saccharine variety to one 
with cleavage facets of J inch across. The band to east of llaondi contains a very large 
amount of wollastonite. In fact the rock is entirely composed of this mineral in places, 
constituting there a ‘ wollastonite schist,’ which from its greater resistance to atmospheric 
Wollastonite. 
* Vol. V, P. 19. 
t With traces of manganese. 
% Chiefly minute scales of mica. 
