Oamaru stone is a nearly pure limestone with an off white to bone white color. There are rare scattered brown blemishes within the stone. The stone is accessed through Parkside Quarry in Weston, New Zealand. When finished, shell fragments can be seen in the matrix. Since some of the parts of the “shell organisms” are not shell but their softer structures; these structures may contribute to the softer blemishes, or pitting, on the finished surface.
The quarry has been in operation since the 1860’s and many buildings have been built with this stone in Oamaru and Dunedin as well as other towns and cities in New Zealand. Although the stone is registered as 4-5/10 hardness, it varies quite a bit in the compactness/hardness. The harder compact stone has a much smoother finish.
The stone’s use as a carving/sculpture medium is well known. When the stone is sanded smooth and blown free of the carving/sanding dust it is easy to see the imbedded shell fragments . If the object is to be for an exterior display then a silicone coating will offer protection against acid rain and mildew/moss. Carving the stone is a process in patience.