Page:Transactions NZ Institute Volume 15.djvu/485
Calcite.—Thames. The terminal end of a large scalenohedron on which an incrustation of small rhombohedral crystals has formed.
Calcite with Aragonite.—Seacliff, near Waikouaiti. A number of small obtuse rhombohedron built up, one on the other, giving the whole crystal the appearance of a hexagonal prism with serrated edges, and with terminal rhombohedral planes. It is in a cavity in basalt.
Calcite.—Seacliff. A similar specimen to the last, but less perfect.
Calcite.—Cape Rodney. A block of white rhombohedral crystals of large size.
Smoky Calcite.—Cape Rodney. A slab of beautiful rhombohedral crystals of calcite of a smoky colour.
Calcite (Dogtooth Spar).—Tararu Creek, Thames. A large slab of breccia with acute rhombohedral crystals of a pale yellow colour on the face.
Massive Crystalline Calcite.—In this form calcite is of common occurrence as veins traversing many different sorts of rocks. It notably occurs in the slate of the Tokatea Range at Coromandel, and in the mines of the Thames, where, owing to its decomposition in contact with acids, the carbonic acid gas is formed which is found in such large quantities at the lower levels of the mines, sometimes rendering futile all attempts at ventilation. It is also frequently met with as large veins in the Maitai limestone of lower carboniferous age both in Nelson and Otago, and again associated with the crystalline marbles of the West Coast and Collingwood. It has also been found, under most interesting circumstances, in some of the granites of the West Coast Sounds, where it occurs as large rhombohedral masses entering into the composition of the rock as an accessory mineral.
Marble.—Some very fine deposits of marble occur in New Zealand, in Caswell and Milford Sounds on the West Coast, as mentioned by Dr. Hector (Report of Explorations of West Coast of Otago, "Provincial Gazette" and Jurors' Rep. N.Z. Ex., 1865, p. 3), and in the former locality a quarry has been opened out by a newly-formed company. The better varieties are of a pure white colour and saccharine texture; they are reported by Mr. McKay to occur moderately free from joints, and to be obtainable in large blocks (Geol. Rep., 1880–81, p. 115). There is also a coarser crystalline variety, as well as a black-veined marble, which occurs in considerable quantities. Marble of good quality again occurs at Collingwood and on the Riwaka Range between Takaka and Motueka, and a crystalline limestone, frequently called marble, is also found associated with the lower carboniferous rocks, and is met with in Nelson; the Blue Mountains, near Palmerston, Otago; and in the Clent Hills, Canterbury.