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The Pamphlet Collection of Sir Robert Stout: Volume 87

Oamaru Stone Quarrying and Export Co., New Zealand. — Oamaru Stone

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Oamaru Stone Quarrying and Export Co., New Zealand.

Oamaru Stone.

The Oamaru Stone is a white granular limestone. According to the Government Analyst, its chemical constituents are as follows:—
Carbonate of lime 90.15
Alumina 1.55
Oxide of iron .55
Soluble silica .45
Insoluble matter 7.15
Loss .15

This places it in the same class as the Oolites of England and the Caen stone of France.

The Oamaru Stone has a remarkable uniformity of colour and texture, and can be obtained in large blocks. Like all Limestones of this kind, it is quite soft when quarried, but hardens rapidly on exposure to a dry atmosphere. This enables it to be worked into the most elaborate ornamentation at little cost.

The stone is rather porous for use in a damp situation, but it answers well in ordinary walls and columns in a moderately dry climate, and it is unexcelled for internal decorations.

The durability of the Oamaru Stone has not yet been thoroughly tested, its resistance to the disintegrating action of sulphate of soda is comparatively feeble, and some of the stones in the page 4 Colonial Bank building, Dunedin, erected in 1865, are showing symptoms of decay. On the other hand, many older structures in Oamaru are as fresh as when erected. The decay in the Colonial Bank is attributed to the stones having been subjected to the action of sea water during shipment at Oamaru and Moeraki. It is not, however, known for a certainty that the stones referred to were so subjected, and I am not clear as to whether the water would have the effect of causing disintegration after such a lapse of years. I am inclined to think that the decay is caused through these particular stones having been of an inferior quality to begin with, and that due care was not exercised in laying them on their natural bed.

G. W, Blair,

M. Inst., C.E.