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DIAMONDS. 17
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Malcolmson, and Voysey, have all left on record accounts of them.
-Mr.
King's already mentioned report containing the latest and most
authentic account of them, it will be best, perhaps, to quote from it a
few passages verbatim, at the same time stating that Mr. King refers
those who are likely to be specially interested to Dr. Heyne, for an
account of the mines as they appeared in his day.
Mr. King writes :—
The
quartzites of the Banaganpilly group form a cap, resting uncomformably
on the denuded surface of a much older set of shales and traps with
some limestone bands. .... The quartzite covering is from 20 to 30 feet
in thickness ; and it is pierced here and there over the Banaganpilly
end of the hill, by shafts of 15 feet or less, from the bottoms of
which nearly horizontal galleries are run to get at the seams of
diamond gangue. The capping is composed of compact grits and
sandstones in thickish beds above, and somewhat thinner bedded towards
the bottom.
Externally the rocks are hard and vitreous. At the level of the galleries there are beds of coarse pebbly conglomerate, occasionally a breccia, which
are sandy and clayey, and with these run seams of more shaley and
clayey stuff. There is no trace of the clayey constitution on the
outside along the outcrop, nor are there any distinct bands of shales
; there are only some sandy shales
down at or near the bottom of the series.....
In
the mines the coolies were picking out a seam of about six or eight
inches in thickness, occurring with thicker and harder beds of
sandstone, and which they said was the diamond layer; this rock when
brought to light turned out to be an easily broken up damp clayey
conglomerate and partly breccia, of small rounded fragments and
pebbles of black, red, green, and pale-coloured shales and cherts, and of quartzite with large and small C
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