PART 1.] 
Mallet: Geological Notes. 
4.3 
Accessory Minerals : Lepidolite. —Accessory minerals are not very numerous. Amongst 
those which occur, the most abundant is lepidolite, which, although not widely distributed, 
exists in considerable quantity where it does appear. I first observed it in a dyke a little to 
the south-west of Pilira, where the granite is composed of white felspar, quartz, and irregular 
masses of lepidolite occurring as a scaly aggregate, varying in color from violet-red to greyish- 
violet. The mineral is also found of a lead-grey and violet-grey color, mixed with quartz, 
An analysis of the violet-red variety by Mr. Tween yielded the following results : — 
Silica ... 
... 
50:19 
Alumina 
... 
... 31-63 
Oxide of Manganese 
... 
tr. 
Lithia ... 
... 
3-71 
Potash ... 
... 
1-40 
Soda 
5-80 
Fluorine 
5-00 
Loss on igniting 
... 
4-23 
102-16 
Small black grains and crystals of tinstone are occasionally discernible in both the 
above varieties. Lepidolite is also met with in a dyke a little to the south-east of this locality; 
also just north of Bhu 1 ad i, and again about a mile south of Manimundar, where the sides 
of a hillock are strewn with Mocks, one of which was estimated to weigh about 8 cwt. 
Green and blue Tourmaline. —At the two first-mentioned localities associated with the 
lepidolite is tourmaline, which varies in color from green to iudigo-blue ; some crystals being 
blue in the interior and green externally. The prisms chiefly traverse, parallel to the 
cleavage, the plates of a silvery mica (altered muscovite?) which is present as well as the 
lepidolite; they also penetrate the quartz. 
Beryl , garnet, apatite, leucopyrile. —Small crystals of yellow beryl are abundant in a 
large dyke which crosses the Tend wall a Nadi south of Mahabar hill; and garnets, generally 
much decomposed, are not unfrequently met with here and elsewhere. The few obtained, in 
which the form was apparent, were trapezohedrons. In three or four dykes a crystal or two 
of green apatite was observed; and from a dyke crossing the S a k r i above S a n k h I 
obtained a mass of leueopyrite, weighing about three-fourths of a pound. 
Tin. —Most of the above minerals being frequent associates of tinstone, their occurrence 
led me to keep a shai-p look-out for such, both in the granite itself and in the river beds. 
With the exception of that disseminated through the lepidolite of Pihra, I ouly observed 
the mineral in one locality however. This was in a lenticular pocket of granite, included in 
mica-schist, at Simratari, west of Pihra, through which a few crystals of g inch across and 
less were scattered. The Occurrence of tin, even in such minute quantity however, is interesting, 
as showing that the same mineral association which has been observed in other parts of the 
world obtains here also; and indicates at least the possibility of the ore being found in larger 
amount in the granite of the area yet to be examined. I fear the chance is hut small of its 
being obtained in workable quantity. The tin-ore of Leda, as previously mentioned, occurred 
as a bed in the gneiss of the metamorphic series. 
Galena. —Galena is very sparsely disseminated through a granite vein, penetrating 
the limestone and associated beds in the Patru Nadi as well as through the latter beds 
themselves. 
Trap Dykes. —Two or three trap dykes were observed intersecting the granite south of 
Gawan. Whether these be of the same age as those which traverse the metamorphic and 
