Page:Transactions NZ Institute Volume 15.djvu/495

is white, with glossy conchoidal fracture like milk-opal, or with earthy fracture like magnesite. At Te Tarata siliceous deposits in terraces cover about three acres of land.

Corundum, …Al.—Dr. v. Haast mentions the occurrence of the variety sapphire from the western slopes of the Southern Alps (Geol. Rep., 1870–71, p. 94), and in August, 1871, Captain Hutton brought another specimen from Collingwood, which is now in the Colonial Museum. It is described in the Seventh Museum and Laboratory Report, p. 18, as follows:—"A tough sapphire, sent by a digger, who found it with alluvial gold at Collingwood, Nelson, is the first discovery of this precious stone in the colony. The specimen, which weighs 336.9 grains, is in the form of a water-worn pebble, remarkable on account of its deep blue colour on the fractured surface, and its great weight; but it is so traversed by fissures as to be of no value as a gem. Its specific gravity is 3.869."

Silicates and Aluminates. ${\displaystyle \scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}}$	Silicates of magnesia and lime, hydrous and anhydrous.
	Silicates of alumina, hydrous and anhydrous.
	Aluminates of magnesia and glucina.
	Silicates of glucina, zirconia, thoria, and yttria.

Wollastonite, Ċa S̈i.—Specimens of a massive form of wollastonite were collected from the Dun Mountain by the late Mr. E. H. Davis in 1871, and are now in the collection of the Colonial Museum. They have been described and analyzed by Mr. Skey, who reports (Col. Mus. & Lab. Rep. vi., p. 15) that the four specimens examined had the following composition:—

	1.		2.		3.		4.
Silica	48.01		49.30		50.62		58.80
Lime	46.20		45.91		44.83		24.60
Magnesia	traces		.80		traces		1.60
Alumina	1.45		1.41		1.84		${\displaystyle \scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}}$12.20
Iron oxide	traces		traces		1.64
Loss	2.19		1.19		traces		1.40
Water	2.15		1.39		1.02		1.40
	100.00		100.00		100.00		100.00

The iron oxide in Nos. 3 and 4 is the protoxide, and No. 4 contains traces of chromium.

They are massive, confusedly crystalline, colour pure white, lustre pearly inclining to vitreous on certain fractures, easily fusible to glassy bead with no soda reaction. Easily decomposed by hydrochloric acid with the formation of gelatinous silica; hardness 4 to 5. No. 4 is an impure