of
the proved outcrop are 300 and 200 yards respectively. The intrusion is
considered to be a dyke, but it is also probable that the injection was
in the form of a sill. The strike is N.E.—S.W., and swings round to
N.N.E.—S.S.W. and E.N.E.—W.S.W. The well-known mines at Tawmaw are the
Dwingyi and the Kadondwin. Besides Tawmaw dyke, there are also a few
other dykes of jadeite rock. Jadeite also occurs as detrital boulders
in Tertiary conglomerates.
Mining
There
are different kinds of mines: outcrop mines of (1) Dwingyi and (2)
Kadondwin. The Dwingyi is the more important and consists of shafts and
tunnels driven along the dyke, and few other old workings are also
present. The jadeite was almost found at the surface with only 3 to 4
ft. of overburden. Serpentine was practically absent. Jade mining is
done only for about three months a year from March to May, and the
advent of the monsoon puts a stop to all activity. After the rains, the
water has to be pumped out, which continues till the end of February.
In addition to the indigenous bamboo pumps, steam pumps are also used
nowadays. Then the mud, debris, etc., are removed and regular mining is
started. In the Dwingyi mine, compressed air drills are used. Work is
also carried on with blunt chisels, wedges and hammers. The tools soon
get blunt as jadeite is tough and hard. The jadeite is also cracked by
burning charcoal. The Kadondwin is worked on more modern lines. (For
fuller details see Chhibbe'r's Mineral Resources of Burma, pp. 46-47.) The mining industry at Tawmaw is gradually declining on account of the increasing depth of the mines.
Indigenous Methods of Working
When jadeite occurs in detrital deposits, surface workings are also done in the Tertiary conglomerates. Some of the
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