Page:Transactions NZ Institute Volume 15.djvu/513

I have since examined these specimens, and find the following sections of crystals, which confirm Mr. Skey's determination:—

The hardness of the mineral is about 7, and it occurs in the more quartzoze portions of a syenitic gneiss, associated with garnets, pyrrhotine and chrome mica, as other accessory minerals.

Tourmaline, n …R S̈i + Ṙ³ S̈i, is mentioned by Dr. Hector in the granite and gneiss of the West Coast (Jurors' Rep. N.Z. Ex., 1865, p. 266); by Dr. v. Haast, in granite, at Mosquito Hill on the West Coast (Jurors' Rep. N.Z. Ex., 1865, p. 257), and by myself in micaceous and hornblende schists at Resolution Island (Geol. Rep., 1874–76, p. 31). There are some very fine specimens of schorl in chlorite schist, from Collingwood, in the collection of the Colonial Museum, arranged as long, black, striated prisms in broken strings which radiate from a centre; they vary from a sixteenth of an inch to a quarter of an inch in diameter. Some very beautiful little acicular crystals in quartz, from Bedstead Gully, Collingwood, are also in the collection; they are of a deep black colour, and red by transmitted light. A blackish green variety also occurs in the granite of Tata Island, Nelson.

Hectorite.—This mineral is described (Col. Mus. and Lab. Rep. xv.) as an altered form of augite, but is more nearly allied to the hydrous silicate of the Serpentine Group. As, however, it does not correspond in composition with any described mineral, I have given it the name of Hectorite.

Its composition, as determined by Mr. Skey, is—