Perhaps the most important geological deposits are those that we use for building purposes. These come from all geological environments. The most important economic factor for building materials is that the material has to be close to where it is going to be used, as the highest cost is in its transportation. Building materials are by far the lowest cost geological materials and their value is usually in the order of only a few dollars per ton.
Crushed rock (commonly referred to as aggregate) is the most commonly used building material, along with concrete which is derived from crushed limestone. Bricks are made from fine aggregate along with clay which acts as the binding material, and iron oxide minerals for colouration. Aggregate is also used as a sub-surface lining on our roads. Plaster is derived from crushed and refined gypsum.
Dimension stones are much higher-value building material and are used as decorative facings on buildings. By far the most commonly used dimension stones are marbles.
In Sydney, the most valuable dimension stone is Hawkesbury sandstone which was used by the early settlers. The expansion of Sydney and the protection of sandstone habitats by the creation of national parks in the Sydney region have meant that this sandstone is now becoming rare and commands high prices (up to $10 000 per square metre).
Other widely used Australian building stones include granite from the Bathurst region in New South Wales, Marble from Angaston in South Australia and black gabbro from Black Hill, north-east of Adelaide, South Australia.
Many of the buildings and monuments (both old and new) in Sydney use natural dimension and carved stone of various types.