Art. XLIX.—On certain Rare Minerals associated with the Tin-ore of Stewart Island, With Notes on their Mode of Occurrence By William Skey, Analyst to the Geological Survey of New Zealand. By Alexander McKay. [Read before the Wellington Philosophical Society, 10th July, 1889.] Towards the end of last March a large and valuable collection was submitted to me for examination. It comprised numerous minerals and specimens of rock-masses which were collected by Mr. McKay, during his recent survey of Stewart Island, from the stanniferous deposits and other rock-formations of the island. The results of my investigations I briefly communicated from time to time, as obtained, to the Director of the Geological Survey; but, as there are many interesting points in connection therewith which have not been treated of in those communications, and which should be made public, I have thought it proper to address myself to this Society in a paper which shall deal with the whole subject. The following are the full particulars of the results of my investigations of Mr. McKay's collection to date. The precise localities of the minerals that I shall describe, and certain interesting particulars as to their mode of occurrence, will be given as a sequel to this paper by the collector of the specimens:— Beryl (Silicate of Alumina and Glucina).—This mineral as exhibited to me is in broken crystals belonging to the hexagonal system. Their cleavage is obviously basal. The diameter of the largest crystal is 1½in., and the length of the fragment in the direction of the longest axis is 1¼in. Colour, pale-green; subtranslucent; hardness, 8. Fluor-spar (Fluoride of Calcium).—Highly crystalline; crystals derived from the cube. Colour generally pale-green; some parts colourless. The coloured parts exhibited vivid phosphorescence when gently heated. Analysis. Fluorine 48.12 Calcium 51.19 Loss (impurities) 0.69 100.00. Tourmaline (Silico-borate of Alumina).—This specimen was handed to me by the collector as tourmaline, and it proved to be the ferruginous variety. It is black in mass, light-brown in powder. Occurs as columnar aggregations in quartz.