Oamaru stone, sometimes calledwhitestone,[1] is a hard, compactlimestone, quarried atWeston, nearOamaru inOtago,New Zealand.
Oamaru stone was used on many of the grand public buildings in the towns and cities of the southernSouth Island, especially after the financial boom caused by theOtago gold rush of the 1860s. Initially used primarily in Oamaru itself, it became popular in Dunedin in around 1866, with theUniversity of Otago'sRegistry Building being the first major structure in the city to make use of it.[2]
The city ofDunedin and town of Oamaru both have many fine examples of Oamaru stone edifices, such asSt Patrick's Basilica. The stone was used widely on buildings in many parts of New Zealand, including in the construction of both the Town Hall and the Chief Post Office inAuckland.[3]
The stone has been prominently used in combination with the more hard-wearingbluestonebasalt found in many parts of the southern South Island, creating a distinctive style of dark grey basalt walls with lighter Oamaru stone facings. Notable buildings to use this combination include theDunedin Railway Station,Otago University Registry Building,Dunedin Law Courts, andChristchurch Arts Centre. In Oamaru itself the stone is most commonly found as the primary construction material, with many of the town's more notable buildings (such as theWaitaki District Council building) showing its distinctive creamy colour.
Its ease of working also appeals to sculptors and examples of Oamaru stone sculpture can be found throughout New Zealand.
The source of the stone is a 40-metre thick deposit inland from Oamaru consisting ofbryozoan limestone.[4] Oamaru stone is limestone with a uniform granular creamy white consistency and colour. Predominantly (90%)calcium carbonate, trace chemicals within it includealumina (1.5%),iron oxide (0.5%) andsilica (0.5%).[5] Its chemistry makes it similar to theKetton stoneoolite of southern England and France'sCaen stone, though it is considerably lighter in weight[2] at 1.68 tonnes per cubic metre when freshly quarried, and 1.47 tonnes per cubic metre when completely dry.[6]
The stone is porous, making it susceptible to weathering in damp conditions, but sturdy in a moderate to dry climate. It is soft when first quarried, hardening on exposure to air.[5] This, along with its uniform texture, makes it excellent for sculptural and ornamental purposes. The finished stonework has a creamy, sandy colour. It is not strongly resistant to pollution, and can be prone to surface crumbling, but is excellent as a material for internal architectural ornamentation. It is also greatly used for free-standing carvings and sculptures.
