The source of the stone is a 40-metre thick deposit inland from Oamaru consisting of
bryozoan limestone. Oamaru stone is limestone with a uniform granular creamy white consistency and colour. Predominantly (90%)
calcium carbonate, trace chemicals within it include
alumina (1.5%),
iron oxide (0.5%) and
silica (0.5%). Its chemistry makes it similar to the
Ketton stone oolite of southern England and France's
Caen stone, though it is considerably lighter in weight 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. 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. ==See also==