Mining
for the abrasive has been frequently successful, but, although the gem
mining has produced interesting results, there never has been a
financial return to warrant the expenditure for this purpose.
INDIA.
In his recent review of Mineral Production in India for the years 1898 to 1903,a
the Director of the Indian Survey. Dr. T. II. Holland, gives data
supplementary to his special treatise on the occurrence of corundum.
Corundum is widely distributed throughout the Mysore State, and a
certain amount of working is done at several points, though it can
hardly be called mining. There has long been a local trade and a local
consumption in India; but
Doctor Holland doubts if it will ever be profitable to develop the
workings on a large scale, in view of the competition of foreign
corundum and of cheap abrasives like carborundum. The native demand,
that of the old saikagar. or armorer, and the lapidary, is
mainly at a few points like Delhi. Agra, and Jaipur, and has been
supplied by the irregular and casual gathering by agriculturists and
cowherders. The data of production in Mysore are very variable and
evidently imperfect, ranging from 28 tons to 150 tons, worth from about
£.100 to £700.
C'EYLON.
With regard to corundum in Ceylon, the Report of the Mineralogical Survey of that Island for 1904,a
by the Director, Mr. A. K. Coomeraswamy. gives quite a full account,
divided into two sections, one on corundum for abrasive use, and the
other on the gem varieties. The first part deals in some detail with
the occurrence of blue crystals in the soil at Haldummulla, mentioned
in Mr. Coomeraswamy's paper on the Rocks and Minerals of Ceylon.'' The
crystals on the Haldummulla estate have been traced over a considerable
area to the foot of a steep jungle-covered bluff, impossible to explore
without heavy cost, but clearly the source of the loose corundum. The
crystals are accompanied over the area examined by pieces of the
matrix, which is sillimanite rock with garnets, containing corundum
crystals identical with the others. Ortho-clase inicroperthite is
associated to some extent, and a little of either rutile or ilmenite,
but these never appear together.
The
second part of the report, on the Ceylon gems, is the fullest that has
appeared for some time. The gem corundums of Ceylon are obtained
entirely from gravel beds, together with lower grades of corundum and
also spinels, zircons, tourmalines, beryls, topazes, etc.. that have
long been known as Ceylon gems. Most of these are supposed to have come
from the intrusive granite rocks of the Balangoda group, but tourmaline
alone has actually been found in a granite matrix on the island. The hills
and ridges are so covered with jungle that it is well nigh impossible
to trace the sources of the minerals brought down by the streams. The
gems and other heavy minerals thus transpoi-ted are to a large extent
very local in distribution, indicating that their sources are in many
small outcrops.
The " gemming " industry of Ceylon is described at some length, with maps and illustrations. The stones are all found in a bed. or sometimes in two beds. of rounded quartz pebbles and cobbles, called "illam," which
is widely distributed through the valleys and lowlands beneath a more
or less thick deposit of alluvium of varying character. The illam is sometimes above the level of the
a Geol. Sun'. India, vol. 32. pt. 1. 1005. p. 105. Sec also vol. SO. pt. ?,. VMM, p. 109. b Ceylon Administration Repts.. 1904; Mineralog. Survey, pp. El. V<:\, Mil. and K-19. c Rocks and Minerals of Ceylon, Spolia Zeylaniea, vol. 11, pt. '.), 1905, pp. 50-00.
