Page:Transactions NZ Institute Volume 15.djvu/496

wollastonite passing into scapolite by substitution of alumina for lime. It is a green-coloured mineral, quite amorphous, and occurs coating one side of a tough light green rock, probably jade.

Chrysolite (Olivine), (Ṁg, Ḟe)² S̈i.—The first mention of the occurrence of this mineral in New Zealand is by Dr. Hector (Jurors' Rep. N.Z. Ex., 1865, pp. 266, 418, and 437), who states that it is of frequent occurrence in the basaltic rocks of Saddle Hill and elsewhere, and also occurs in Milford Sound. It is again mentioned by Dr. v. Haast (Jurors' Rep. N.Z. Ex., 1865, p. 257) as grains in the basaltic rocks of Banks Peninsula, and (Trans. N.Z. Inst., vol. i., p. 180) as large concretions in basaltic rocks from the Chatham Islands, and (Geol. Rep., 1870–71, p. 29) in the basalts of the Hurunui and Mandamus districts. R. Daintree, Esq., F.G.S., refers to its occurrence in dolerites from the Selwyn River, Snowy Peak Range, Flagstaff Hill basin, and Hororata district, (Trans. N.Z. Inst., vol. vii., p. 458); Professor Liversidge also describes a specimen from Dunedin as brown-coloured imbedded grains (Trans. N.Z. Inst., vol. x., p. 497), and I have noticed small grains of this mineral, green and brown in colour, in many microscopic sections of basaltic and doleritic rocks from various localities.

Dunite.—This mineral is a massive variety of olivine through which grains of chromite are scattered. A specimen from the Dun Mountain, Nelson, was first described by Dr. v. Hochstetter (New Zealand, 1863, Eng. ed., p. 474) as follows:—"It consists of a very peculiar kind of rock, of a yellowish-green colour when recently broken, but turning a rusty brown on the surface when decomposing. The mass of the rock is olivine, containing fine black grains of chromate of iron interspersed; it is distinguished from serpentine, for which it was formerly taken, especially by its greater hardness and its crystalline structure. I have called it Dunite." Analysis of dunite by R. Renter (Lab. of the Polyt. Inst. of Vienna):—

It is again mentioned by Dr. Hector (Jurors' Rep. N.Z. Ex., 1865, p. 411), who adds to Dr. v. Hochstetter's description, that it possesses a flaky structure, conchoidal fracture and hardness of 6; and he also mentions its occurrence at Milford Sound, where it passes into jade. He again alludes to it (Trans. N.Z. Inst., vol. ii., p. 377), stating that at the Dun Mountain it appears at the surface as a large mass several miles in extent. It has since been discovered at Jackson's Bay, by Mr. D. Macfarlane, associated with serpentinous rocks (Geol. Rep., 1876–77, p. 27).