April 2, 1900.] THE TROPICAL AGRICULTURIST. 
657 
MICA -MINING IN BENGAL.* 
Different Kinds of Mica, Size of Siief.ts 
AND Values. 
By A. Jfei-vyn Smith, M. Inst. 3fJL 
Position. — The mines described are sitnated between 
85 deg. to 86 deg. 30 min. east longitude, and 24 deg. 
25 min. to 25 deg. north latitude. The country ia made 
up of a series of parallel ranges of low hills some 400 ft. 
above the surrounding country and 1,200 ft. above sea 
level. The direction of the ranges is east and west 
nearly ; they form the boundary between the Hazari- 
bagh district on the south, and the Gaya and Monghyr 
district on the north, being part of the Bengal Presi- 
dency, India. 
Geology. — The country is made up of gneiss, grading 
into mica schists, tourmaline schists, hornblende rocks, 
qnartzites, and a course felspathic rock resembling 
conglomerate with intrusive dykes of fine-grained 
diorite. The hornblende rock closely resembles the 
diorite, and weathers into similar rounded boulders. 
But this variety passes into a much coarser kind, in 
wliioh " blebs " of white felspar are so close-placed as 
to give it a " banquet " appearance. The mica schists 
are strongly developed in this area, and are made up 
chiefly of white mica (muscovite) with here and thero 
a little black mica (viotite) and red mica (lepidolite). 
This rook is highly schistose, breaking up into thin 
laminse, and consists chiefly of small plates of mica, 
cemented together, with a slight admixture of felspar 
and quartz. It is this rock that contains the lodes 
that yield the mica of commerce. The gneiss and 
other foliated rocks have a nearly east and west strike 
(about 5 degrees north of east and south of west), and 
underlie to the north at an angle of about 75 degrees. 
These rocks are classed in Indian geology as among 
the younger gneisses. 
Pegmatite Veins. — Running with the bedding of the 
schists, from east to west, are numorous veins of 
granite (pegmatite) varying in width from a mere 
thread to 20 ft. The schists are in places faulted or 
thrown out of their normal strike. The pegmatite 
veins are subjected to the same "faulting," and fre- 
quently at the point of " faulting " short north to 
south "veins or "cross courses " of great width have 
been formed. 
The veins are made up of amorphous masses of 
quartz, large crystals of pink felspar (orthoclase), and 
crystals or " books " of mica (muscovite). The quality 
of the vein varies with the nature of the adjacent rock. 
Near to the quartzites, the vein stuff is nearly pure 
quartz with little felspar and mica. Where the adja- 
cent rock is highly felspathic, pink felspa-r crystals 
are the chief consfitueuia of the lode ; while we may 
look for a huge predominance of mica, where the in- 
cluding rock is mica schist. This fact is of importance, 
as a knowledge of this peculiarity of segregation iu 
the vein matter enables the miners to disci-iminate 
between the spots that will yield more rr less mict*. 
In addition to thes^ three chief constituents of the 
pegmatite vein?, the following accessory minerrJa are 
sometimes found — tourmaline, garnet iin-stone and s, 
colunibite. The tourmaline is at timds strongly de- 
veloped. Near to tk3 tourmaline schists, large mif!=iiTo 
crystals of black tourmaline are not infrequent in the 
lode, and occasionally crystals of tourmaline penetrn'e 
the mica books across the planes or laminaticii ..ud 
destroy the value of the sheets. 
The pegmatite viens iu this district are apparently 
of aqueous origin and due to segregation. The fol- 
lowing are some of the data pointing to this conclusion. 
l.In many places the veins die out in depth and in 
length. 2. The vein matter partakes of the quality of 
the including rock, quartz, felspar, and mica pre- 
dominating as the lode traverses rocks containing 
these minerals in excess, 3. The crystallisation of th« 
vein matter varying within very short distances not 
being at all homogeneous, as one would expect in an 
igneous dyke. In places the crystals of mica are 2 ft. 
* Paper read before the lastitiitioa of Mining and 
Metallurgy. 
82 
long, 18 in. wide, and 9 in, thick. Within a iew 
hundred feet of either side of this spot the mica books 
are small und worthleso. 
Ages of the Minet. — Tho zone of mica-bearing rock 
has been worked for centuries by the HindooB. Mica 
is largely used by them for ornamental purposes, 
such as inlaid work, tassels, flower, toys, and bannori. 
The large clear plates are much used by native artists 
for portrait painting, as being extremely durable and 
not affected by heat or damp and impervious to the 
attaks of insects. The waste mica is ground to a coarse 
powder, and after being mixed with starch is applied 
to cheap cotton cloths to give them a sheen. 
The great marts for mica for native consumption 
are Patna and Delhi. Dr. P. Breton, who visited 
these mines in 1826, found as many as 6,000 people At 
work at different mines. In 1849 Dr. McClelland give* 
the output as 100,000 maunds (a maund being 821b.j. 
In 1863 the statistical account of Bengal says 10,000 
maunds were exported. 
'The Nalivt Methods cf Mining. -The native mines 
are of the most primitive kind. Open cute along the 
outcrops of the pegmatite veins where hooka of mica 
are seen in any quantity. These outs are continued 
down 20 ft. or 30 ft. till the sides become dangeroin. 
No timbering is used to keep the sides from falling in, 
and frequently accidents happen and the miners ara 
burisd beneath the fallen walls of the reef. \Vhero 
exceptionally rich stuff is met, and the vein-stuff ia de- 
composed and soft to some 50 ft. or 100 ft. inclines are 
put in, and follow down the rich shoots of mica in • 
most tortuous course, zig zaging about from side to 
side with the ''leads" of rich ground. Long lines of 
women, near to each other and pLioed in double ro* 
from the warter level to surface, hand out earthern 
pitchers— called " gurrahs " — to one another ; the full 
pitchers are handed up one line and the empties 
down the other. As many as seventy women are 
sometimes placed to remove the warter from a mine 
not 35 ft. deep in perpendicular depth. The incline, 
of course, vt'aa much mora than this iu length. 
Where the reef is highly felspathic and of large 
size, decomposition extends to a quite hundred feet or 
more, and it is here that their largest mining opera- 
tions are carried on. In order to ventilate the in- 
clines and draw out the mica, perpendicular shafts, 
about 2ft. in diameter, are put in. The author counted 
as many as thirty ot these circular shafts along the 
strike of the reef, and within a few feet of each other. 
The miners are a local tribe called "Bandathis"; 
the men, Vi/omen and children ail working at the mine* 
when they have no agricultural work in the fields. 
Work is only conducted in the dry months (NoTember 
to May). Immediately the rains set in they return to 
the tillage of their fields. Work is only condutoted' 
in the day, beginning about 8 a.m., and giving over 
at dusk. Whan the veins are hard, yet sufficiently 
rich to pay for the labour, large fires are kindled 
agiuet the face of the lode, and when the vein stuff 
is sufficiently heated, water is thrown on to it, when 
the sndden cooling causes the rock to shrink and crack. 
In these cracks \vedgea of soft iron, locally manu- 
factured from the magnetite iron eres common in this 
neighbourhood, are driven and large boulders detached. 
The exposed books otmica are chiselled out and taktn 
to surface. The books of mica are split into sheets of 
about |in. in thickness. All tho rough edges and flaws 
are trimmed of by means of a sharp sickle fcalled 
" hasawah '), and then sorted according to colour and 
size. The sheets are in some cases very large, 24 in. 
by 18 iu. being the largest in this district. In tho 
Itakuri Mine, Nellore district, Machaa, plates 60 In, 
by 40 in, have been obtained. 
Present Method of V/orh.— It is only within very 
recent years that Europeans have taken to the mica 
industry. Mining is still conducted on purely native 
methods described above ; and although 250 mines ara 
at work in this districit, on not a single one is 
machinery of any kind used, and certainly on none of 
the properties yisited by me this year (1898) was 
there the least attempt at European methods of 
mining. The same wasteful, slow, and laborious 
system practised by the natives for hundreds of years 
