Page:Transactions NZ Institute Volume 15.djvu/486

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Madrepore Limestone.—At Reefton a limestone occurs, chiefly composed of large madrepore corals, which if cut and polished would afford a most beautiful ornamental stone.

Lithographic Limestone.—A stone suitable for most classes of lithographic work has been found in considerable quantities at the Abbey Rocks, Westland, and again at Amuri Bluff; but at the latter locality it is too much traversed by joints to be of any value.

Chalk.—Dr. Hector mentions (Trans. N.Z. Inst., vol. ii., p. 178) the occurrence of chalk with flints on Campbell Island, and during 1880 a deposit of chalk, not less than 100 feet thick, was discovered at West Oxford, Canterbury, of which Dr. Hector says (Geol. Rep., 1879–80, p. xviii.): "The samples of chalk obtained have more perfectly the mineral character and texture of English chalk than any previously discovered in New Zealand. The rock is pure white, fine-grained, and soft enough to be used for the manufacture of crayons.

"Its composition as determined by analysis is as follows:—

Calcic carbonate  82.36
Magnesic carbonate   1.84
Ferric oxide traces
Silica  15.69
Water   0.21
100.00 ."

Stalactites and Stalagmites occur in all the many limestone caves of New Zealand, some of them being of great size and beauty. Of these the caves at Whangarei, Waipu, Collingwood, and Mount Somers are well known for the variety in form and size in which these deposits of lime occur.

Travertine.—Dr. v. Haast mentions (Jurors' Rep. N.Z. Ex., 1865, p. 256) a deposit of travertine from calcareous waters at the Weka Pass, and it occurs on a small scale in many localities, but no large deposits are known.[1]

Limestone occurs very widely distributed throughout New Zealand in all degrees of purity and texture from a marl with 4 or 5 per cent. of carbonate of lime to a limestone which is nearly pure. Hydraulic varieties also exist, and at Mahurangi a deposit of this sort has been worked for some time past.

Aragonite, Ċa C̈, is by no means of so common occurrence as calcite, but has still been found in a few localities. Dr. Hector mentions it (Jurors' Rep. N.Z. Ex., 1865, p. 266) in cavities in basaltic rocks at Dunedin, and

  1. ↑ A remarkable deposit of this mineral occurs on the Alfred River, a branch of the Maruia River, in terraces which are in the aggregate about 400 feet in height. They are chiefly composed of moss which has been petrified by the calcareous waters, and are now partially clothed by a fresh growth of this moss.
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