Nov. 2, 1903.] THE TROPICAL 
AGRICULTURIST. 
355 
The Canadian mica consists of a silicate of 
magnesia, and is usually colourless or brownish 
yellow. It is very soft, and possesses excellent 
properties for use as insulators in dynamo commu- 
tators, and for other electrical work. The other 
variety, know as bistite, contains as a rule a 
quantity of iron, and is very rarely found in a 
colourless form. Some varieties are black and 
others dark green. In India this species of mica 
is largely used as a drug, when powdered by the 
Datives, and is supposed to be very efficacious in 
cases of diarrhoea or aysentery. 
Mica was much valued by che ancients, both 
in India, and also by the prehistoric tribes of 
North America. The mica of the B:iziriba:^h 
and Nellore Districts has been worked for centuries 
by the Hindus, who used it in ages past, as now 
for ornamental work, such as tassels, llawers, and 
also for inlaid work. L irge sheets were used by 
native artists in the times of the Moguls for 
painting pictures upon, and the art of portrait- 
painting on mica sheets still exists. 
METHODS OF WORKING. 
The methods of working in vogue centuries ago 
are still carried oa by the nscives, usually as large 
open pits and cuttings, which follow the pegmatite 
veins in which the mica occurs as deep as 20 or 
30 feet occasionally, when the rock is soft enough, 
small and irregular inclines are put down, follow- 
ing the direction of the riciiest shoots. Timber is 
hardly ever used to support these excavations, 
and when water is met with in any quantity the 
mine is either stopped or kept under control by 
long lines of workers, usually women, who hand 
out full giirrahs to one another, the empty vessels 
being returned by another line in the same manner. 
In North Carolina in the United States mica 
mines were wrought in prehistoric days hy the 
Indians, and the discovery of mica ornaments in 
ancient burial mounds, hundreds of miles from 
the mica districts, led to investigation, and finally 
to the re-openiug of the old excavations in the 
Alleghany Mountains, the nature of which had 
puzzled antiquarians for many years. As in India 
the ancient American tribes used the mica for 
ornamental purposes, chiefly in connection with 
their leligious ceremonies, 
THE USES OF MICA. 
The uses of mica at the presenc day are multi- 
tudinous. In India a large quantity of the mineral 
produced goes to Delhi and Patna, where it is 
chiefly worked up for native ornamental purposes. 
The earliest industrial use of mica was prob ibly 
for windows and lanterns, but it is rarely used for 
these purposes nowaday.?. 
It is very largely used for making the little 
windows in heating stoves, but although it resists 
heat admirably, the smoke from coil or oil very 
rapidly impairs its transparency. Mici chimneys 
for lamps are used very generally for oub donr 
purposes, where rapid changes in temparature 
would break glass. The great use for mica has 
been for electrical purposes, as owing to its elasti- 
city and non-conductiug properties, it is one of 
the best available substances which can be obtained 
for placing between commutatov segments. Small 
plates of mica are also manufactured into " mica- 
nite"by cementing tliem together on a cloth or 
paper basis, with an insulating substance sucli as 
shellac. Micanite can readily he moulded into 
various shapes, and is much used for different 
details in electrical machinery. 
Mica cardboard is used for coating boilers and 
steam pipes, being almost as eli'ective as asbestos 
goods for this purpose. It is almost manufactured 
into firemen's helmets and solar topees, and it has 
been used to line the interior walls of buildings, 
both for oiuameutal and fireproof purposes I The 
variegated colours of the Jragmenis ^of mica 
cemented into this cardboard, adapts it well for 
decorative purposes, and it is probable that as j 
substitute for ordinary wall papers its use wil 
be much extended. 
Mica waste is ground up into a tiae flour and 
used for putting a glittering surface on wall papers 
etc., waite mixed with oil it has a value as a lubri- 
cant. The explosive known as mica powder consists 
of nitro-glycerine and an absorbent made of ground 
mica, instead of the infusorial earth used in the 
manufacture of ordinary dynamite. 
A RIVAL IN BRAZIL. 
India is Still the chief mica producing country in 
the world, but large and constantly increasing 
quantities are also mined inCitiada and America, 
wuile very iarge mica Districts are novv being 
opened up in Brazil, which bid fair to swamp all 
the other countries. 
The most important district in India is at Haza- 
ribagh in Ohota-Nagpur, where English Companies 
are at work, as well as many native concerns. The 
mica occurs as " book," in pegmatite veins in a 
country consisting largely of gneiss and mica 
schists, European methods have been introduced 
to open out these mica-beariug veins, but as in the 
case of other minerals, skilled management is 
required to make mica mines a successful under- 
taking. The Vellore District of Madras contains 
many pegmatite veins, containing large sized 
plates of mica iu a species of hornblende schist. 
Some of the largest sheets yet discovered have 
come from Nellore. 
Tiie Canadian mica has the advantage of being 
very easily worked, as it occurs in a very soft rock. 
Mica mining in North Carolina, and new Hamp- 
shire in the United States, is a rapidly growing 
industry. A heavy duty oa imported mica helps 
to expand the American output, bat the 
amount used iu the United States is still far 
in advance of the Home production. A quan- 
tity oi mica was formerly obtained from Norway, 
but the deposits were rapidly exhausted and the 
export has uow ceased, Tlie Brazilian mica 
mines have only been at work for about five 
years, but the deposits are practically in- 
exhaustible, and they have the advantage of 
labour which is almosb as cheap as in India, 
and more etfi^ieut, as well as raiUvay coiumani- 
cation from the mining districts to the coast. 
The Brazilian deposits are very like those of 
Bengal, consisting of veins of pegiuatitein schists 
and other metamorphic rojks. Tne best mines in 
Brazil are in the States of Gi»gaz, Bahla, and Miuas 
Geraes, near Kio de Janeiro. Tuey are situated 
on hiUs over 3,000 feet higli and witliin a few miles 
of railways in each instance. The veins are on an 
average 10 feet wide, and produce very large 
plates of excellent mica, often J feet by 12 inches 
when dressed. Tiiese veins consist largely of 
Kaolin, or decomposed felspar, and this product 
also linds a market in Brazil. Much of the mica 
is of the ruby variety, and readily commands 
the hignest prices. The mica is picked into bo-^es 
of about I cwt. each, and great care is exercised 
in eliminating a,ll flawed or discoloured sheets. 
