Page:Transactions NZ Institute Volume 15.djvu/471

Napier and Masterton, again, somewhat extensive deposits of the lignite series are met with, in which, however, the seams of lignite are of no great thickness and have received but little attention.

Brown Coal.—The principal deposits of brown coal in New Zealand belong to the cretaceo-tertiary formation, and, as pointed out by Dr. Hector (Geol. Rep., 1878–79, p. 7), they are always at the base of the marine portion of the series in every locality where they occur. They always rest upon the basement rock of the district, marking a great unconformity and a long-persistent land area at this period.

Thus they are overlaid by the Leda marls in the Waikato, the fucoidal greensands at Whangarei, and by the island sandstone in Otago and on the West Coast of the South Island.

They are the most widely-distributed class of coals, being largely represented in Auckland, Canterbury, Otago, Southland, and Nelson.

In Auckland the coal from the Waikato is of an inferior character. It does not stand the weather well, and has a high percentage of water. The average composition of these coals is—

Two mines are at present being worked in these deposits, one, the Huntly Mine, having a seam from 6 feet to 40 feet thick, and the other, the Waikato Mine, a seam from 10 feet to 18 feet in thickness. Besides these, the Bridgewater Colliery, near the Miranda Redoubt, which is now closed, was working a seam no less than 53 feet thick.

In Nelson there are a few seams of brown coal, none of which are at present being worked. Amongst these is a highly-inclined seam at Richmond near the town of Nelson, another at Karamea, and at Charleston, near Westport, a large seam of brown coal occurs over a considerable area of flat country, but is not worked since coal of better quality is near at hand. Taking an average of the analyses which have been made of these coals, their composition is as follows:—