The white, easily sawn Oamaru Stone is known to geologists as Totara Limestone. When Totara Limestone was formed, some 35 - 40 million years ago, the sea covered about 200 sq km of North Otago, reaching as far west as Aviemore.
Hard calcareous shells of marine animals and plants living in the shallow warm seas built up a thick blanket of limey sediment on the sea floor. Over millions of years the soft sediment became lithified (hardened into rock ), and was eventually lifted above sea level.
This Limestone is mostly formed of sand-sized bryozoan fragments, with vast numbers of micro fossils such as foraminifera, and occasional larger fossils of molluscs, brachiopods, corals and echinoderms, and sometimes penguin or whale bones and sharks teeth.
Occasionally a stone carver may come across a brown or soft spot, it is believed to be a branch or other form of wood trapped within the stone.
We often don’t know what we will find in the stone until we begin our work.
In most cases we simply accept any variations the stone throws at us and work it in or around it. There are ways to cosmetically cover any blemishes if we think it necessary.
Durability of the stone
The durability of limestone is often questioned because it isn’t a “hard stone” like marble or granite. The reality is that many old buildings down south are constructed from limestone and still stand today, as are the pyramids in Egypt, so the short answer is that the stone lasts a very long time.
In addition we always seal our sculptures with a water repellent that adds to the look and longevity. It’s a very simple process and we recommend maintaining the sculpture every few years.
CARVING WITH OAMARU STONE
The stone we use is Oamaru stone (also commonly known as Limestone). We use this particular stone because it can be readily shaped, Oamaru stone is a favourite material for stone carvers and sculptors in New Zealand.