Page:Transactions NZ Institute Volume 15.djvu/491

Quartz, S̈i.—The distribution of this mineral in New Zealand in one form or the other is general.

Rock Crystal.—The purest form of quartz is represented in the collection of the Colonial Museum by a clear pellucid specimen from Tamata, and some beautiful little crystals from Kereru, Napier, which were forwarded on the supposition that they were diamonds. These small rock crystals occur in many localities in the North Island, being derived from the rhyolitic rocks, which occupy a considerable area in the Taupo district; and they are again found in Canterbury, where they enter into the composition of the quartz porphyries of Mt. Somers and the Clent Hills; they have frequently been forwarded for examination from time to time on the supposition that they were diamonds. Some very beautiful specimens of rock crystal were collected from the Cromwell Company's Mine last year by Mr. McKay, the crystals being sometimes three-quarters of an inch long and a sixteenth of an inch in diameter, the ends being sometimes pyramidal, sometimes hemihedral, and sometimes tetrahedral; they frequently interpenetrate one another, and two groups of crystals interpenetrate and pass through very flat and perfectly crystallized rhombohedrons of calcite. Some fine specimens from Milford Sound are also in the collection.

Amethyst Quartz.—Some very fine specimens from the Rakaia Gorge, Canterbury, are in the collection of the Colonial Museum, and Dr. v. Haast mentions its occurrence in amygdaloidal trap (Jurors' Rep. N.Z. Ex., 1865, p. 256) and in the melaphyres of Canterbury (Geol. Rep. 1873–74, p. 9).

Milky Quartz.—Dr. v. Haast (Jurors' Rep. N.Z. Ex., 1865, p. 256) mentions it in the granites of the West Coast, and it is of common occurrence throughout New Zealand.

Prase is mentioned by Dr. v. Haast (Jurors' Rep. N.Z. Ex., 1865, p. 256) as small deposits in quartzose porphyritic trachytes at the Gawler Downs.

Jasper.—There is in the collection of the Colonial Museum a specimen from Tinker's Gully, Thames, which is red but gritty, one from Hongikuri, Auckland, also red but gritty, and another from Mahurangi, which is red, with opaline and brown patches. Besides these Dr. Hector has mentioned its occurrence at the Snares (Trans. N.Z. Inst., vol. ii., p. 177), in the volcanic rocks of Moeraki and Otepopo, and the porphyritic rocks of Dunedin Harbour (Jurors' Rep. N.Z. Ex., 1865, pp. 266 and 437), and at Coromandel and Whangaparawa (Jurors' Rep. N.Z. Ex., 1865, p. 253); it is mentioned by Dr. v. Haast from the Malvern Hills (Jurors' Rep. N.Z.