Shell Lime Deposits

New Zealand Journal of Agriculture, Volume 62, Issue 5, 15 May 1941, Page 345

Shell Lime Deposits

-By-

C. WALKER,

Instructor in Agriculture, Thames.

ON the Hauraki Plains and at other points on the Coromandel Peninsula, where lands adjacent to the sea once formed part of the ocean bed, there are fairly considerable patches of sea shell. A , striking feature of these deposits is the depth to which pure shell has accumulated, while the freedom from extraneous material, such as sand and humus, is also noteworthy. In parts, fish bones, traces' of decomposed seaweed, and even remains which appear suspiciously

like those of human origin, are found intermixed with the shell These would no doubt have an appreciable fertilising value .where these deposits are exploited commercially. At three pointsKopuarahi, Miranda, and Whitiangalime works have, been established with a view to converting these shell deposits into commercial lime. The plants at both Kopuarahi and Miranda have outputs of about 12,000 tons a year, and their products are widely distributed throughout the province. The product itself is very finely ground, and, judging by the

natural deposits, it should be very uniform in quality. At Whitianga the output is much less, being nearer a 200 tons maximum in any year, and the output is largely used oh the farm where the works are situated. ' ' - While the deposits are by no means exhausted, those at Kopuarahi and Whitianga are much less than at Miranda, where the shell belt covers an area two miles in length by a depth in places up .to 1-j miles. Moreover, this deposit is being rapidly enlarged by the accumulation of new shell

brought in from the Hauraki Gulf by the sea. ' Being inland, both the Ko - puarahi and Whitianga deposits have no opportunity of being enlarged, and consequently there will come a time when the present beds will become exhausted. , ' ' , \ Generally speaking, farmers hold shell lime in high regard. Naturally, some favour' lime from one deposit more than that from another, but, as it will be apparent that little significance can be attached ,to this very human tendency. What is important, however, is that these deposits of shell are being employed to good advantage. The works are performing a useful function, and are providing a much needed service to the farming ' community