part 1 .] Mallet: Gneiss of South Mirzajrur and adjoining country. 
19 
Felspars. 
Two felspars are often coexistent in the gneiss and in the coarse pegmatite veins by 
which it is traversed* One, orthoclase, generally forms 
the greater proportion of the rock, and is seldom or 
never absent. The usual color is some shades of pink or red, but it passes not unfre- 
quently into pure white. The other, oligoclase, is not a constant ingredient of the rock, and 
where it does occur, it is present in much smaller proportion; it is always white in color, 
weathering with a dull opaque surface from superficial alteration into Kaolin, and on such 
altered face, it is markedly distinguished from the orthoclase which weathers far less readily. 
Oil a fresh fracture the two minerals are less easily distinguished, particularly when the ortho¬ 
clase also is white. The striae characteristic of triclinic felspars are often prominently marked 
on the oligoclase. The following is an analysis by Mr. Tween from a specimen out of one of 
the pegmatite veins:— 
Silica 
.... 66*24 
Alumina 
... 20*72 
Lime 
... 3*56-v 
Potash 
... 2*26 >= Soda 14*65. 
Soda 
... 9*22 ' 
102-00 
Mr. Tween’s determination of the alkalis in similar felspar from Bundlekund gave— 
Soda 
Potash 
13*33^ 
2*76J = ^oda 
Micas. 
The mica is usually biotite, and black or dark-brown in color. It generally occurs in 
small laminae, but occasionally crystalline layers or single 
crystals occur with cleavage faces one-half of an inch or one 
inch across. Muscovite sometimes takes the place of the above, hut it is less common. 
The mica is sometimes associated with hornblende, and thence by gradations the rock 
passes into hornhlendic gneiss. In the gneiss which is associated with the limestone of the 
Bichee Nuddee, large crystals of hornblende two or three inches across occur. 
A yery handsome epidotic rock occurs in a few places, which may perhaps he granite, 
Epidote but ^ never obtained a clear section showing what its true 
relations are. It is found in low hillocks to the south¬ 
west of Pokhra, being there composed of pink felspar and epidote with a little quartz. 
Traces of foliation (or which seem to he such) can be seen, but they are faint. Thin veins 
of epidote with quartz sometimes intersect the gneiss both obliquely and parallel to the 
bedding. Sometimes tho sides of the vein are of epidote, while the centre is of crystalline 
quartz, tho summits of the crystals pointing towards each other with a hollow in the centre 
as if the vein had been produced by infiltration. 
Epidote as a rock in itself has been obtained in only one instance, where it occurs as a 
bed in the gneiss of a few feet thick. 
Of the bands of limestone hitherto met with in the gneiss, the most remarkable is 
that near the mouth of the Bichee Nuddee, a stream which 
falls into the Rehr near Singrowli. The rock, which is a 
white marble, afforded on analysis the following composition :— 
Carbonate of lime 
Limestone included minerals. 
„ magnesia 
* n iron 
Insoluble (chiefly minute scales of mica) 
Total 
, 53*85 
45*78 
*34 
1*00 
100*97 
being, therefore, a typical dolomite. 
