'Transactions of the Bombay Geographical Society, from September 1850 to June 1852. Edited by the Secretary. Volume X.' [‎187] (320/458)

KUNK.UR IN BLUE CLAY,
187
These borings often extend for several feet in a line continuously
they are invariably coated with a lining of pinkish white carbonate of
lime, varying from a few lines to T V of an inch in thickness. Its tint and
texture is not unlike that of some varieties of satin spar ; it is crystalline
throughout, but has evidently been deposited in successive layers, of
which fifteen or twenty may occasionally be counted. It seems
probable that the outermost of these coatings may have been deposited
by the worm which bored the hole—similar borings, but of very much
smaller dimensions, are still found in the decayed specimens of the
root of the mangrove growing on our shores, the calcareous coating
being in this case however as thin as paper, and equally polished on
both sides ; and that this was thickened afterwards by deposits of pure
carbonate of line trom the rain water of the monsoon,^ this
at times going on till two-thirds of the boring are filled up by the
spar. The walls of these tubes are always thickest on the lower
side, especially when the deposit has been considerable, and they are
generally uneven inside: outside they are smooth and polished, con
forming entirely with the shape of the boring which forms the mould.
When found in situ, these tubes are generally filled with portions of
the blue clay from the surrounding beds. This in many cases is
hardened into kunkur of the form of the interior of the tube, of the
texture and substance of the nodules around: in many cases,'the fine
sparry coating has been partially or wholly eaten away or redissolved
by the water, so that nothing but the kunkur core remains. The per
forations and fangs of the roots have frequently been filled up from the
outset with clay, which has become kunkurized, so to speak, furnishing
a cast. It is very seldom that they have any internal organic structure,
though I have met with a few cases of the opposite, so that they are
merely casts and organic in external aspect, and partake in no way be
yond this in the character of petrefactions. The best open section of the
relation betwixt the concrete and blue clay is that on Sewree beach,
where all the characteristics of both formations are fully manifested,
and it will be seen from the litographs that the appearance pre
sented by it is not unlike that of the dirt bed of Portland.
31.—The blue clay with the mangrove roots, and all the other charac-
j nnstics already referred to, is found in all the wells I have met in
% rrn • 1 ~
the .^suggested by Dr. Carter, to whom I have submitted specimens of all
i encrusted borings—it seems to meet the circumstances of the case.