(12) Petroleum and Oil-shales.

Though several localities in the North Island have produced petroleum oil of a fine quality, sufficient has not yet been discovered to render the venture a commercial success.

Three places have been noted for this mineral, viz.:—(1) Taranaki, near the Sugar Loaves; (2) Poverty Bay, east coast, Auckland; and (3) Manutahi, Waiapu, East Gape. From the first-named the oil has a very high specific gravity—.960 to .964 at 60 degs. Fahr. It is a good lubricating oil, but not suitable for an illuminant.

The oil from Waiapu resembles that found in Canada; by three distillations about 65 per cent, of good illuminating oil with a specific gravity of .843 is obtainable.

That from Poverty Bay is a true paraffin oil. That from Rotokatuku is of a very fair quality, with a specific gravity of .833.

So long as twenty-five years ago a company was formed to bore for oil at New Plymouth in Taranaki. A little to the north of the Sugar Loaves a hole was put down for 300 feet by hand-labour, and indications of petroleum were found with a little carburetted hydrogen gas. Another borehole was put down on Mikotahi Island, with about the same result Another company sank a shaft near high-water mark, and at a depth of 60 feet they were driven out by gas, having at 44 feet passed through a porous stratum with a little oil. For a few weeks, it is said, about 50 gallons of oil per week was obtained here. Recently an English company, known as the South Pacific Oil Company, has been boring, and in 1891, the depth attained was 680 feet, A little oil and some gas had been met with, and the boring was proceeding. The oil had a specific gravity of .834, and a flashing point of 93 degs.

The surface of the country is covered by a thick deposit of trachytic breccia, carrying ferruginous seams, and the places where indications of petroleum are met with appear to be included in a belt not more than 500 yards wide. In many wells about the locality small quantities of oil are found, but as yet no commercial success has been attained The borehole mentioned above was commenced 16 inches in diameter, and appears to be carried on by American workmen.

The Southern Cross Oil Company have been boring in the Waiapu Valley, Napier, for some years, and a considerable area of oil-bearing rocks of great thickness has been found. The borehole was in 1886 at 1,700 feet, and it was intended to continue to at least 2,000 feet.

In the Geological Report for 1888 is an account by Mr. Jas. Park, F.G.S., of numerous escapes of inflammable natural gas which exist on the page 57 east coast of Wairarapa North County, in Wellington Province, where there is a belt of oil-bearing strata from 3 to 8 miles wide of Secondary age, and consisting of shattered glauconitic sandstone, slaty shales, and sandstone, indurated marly and brecciated siliceous clays. It is considered, however, that the rocks are too much fractured to afford the requisite pressure for the condensation of the gases. A bonus of 6d. per gallon for the production of kerosene up to 50,000 gallons, in quantities of not less than 10,000 gallons at a time, was offered in 1874 and 1885, but no applications were received,

In addition to natural gases and oils the colony contains several oil-shales, of which the following may be mentioned:—

In the Chatham Islands is a bituminous peat, occurring in detached blocks of irregular form and considerable size, in the superficial gravels, It contains, after exposure to the atmosphere, 20.41 per cent, of fixed carbon, and 66 per cent, of volatile hydrocarbons. A similar mineral is found at the Auckland Islands.

A carbonaceous mineral containing 75 per cent, of volatile matter, and closely resembling torbanite, is found at Awatere, near Auckland.

It is found associated with coal-seams, and an inferior, but somewhat similar, shale has been brought from Blueskin near Dunedin.