Marble is a hard, crystalline metamorphic rock made up of calcite or dolomite crystals. It starts its life deposited as limestone sediment in the world’s seas and during the process of mountain building (or orogenesis) it is subjected to heat and pressure over millions of years. This process is called metamorphosis and it changes the limestone to marble – it’s a bit like the process that happens when you bake a cake in the oven, it begins as a soft wet mixture and ends up as harder, drier cake. In much the same way the limestone is ‘cooked and squeezed’ into marble, as crystals of calcite grow into the tiny spaces in the rock. The length of time the marble takes to cool determines the size of the crystals.
Marble is a marvellous rock for sculptors to work with as it takes a high, lustrous polish and is relatively easy to carve as it is much softer than granite. It has been sought after for use by sculptors over 1000’s of years as a material for statues and monuments; it is also used as a facing stone in buildings and residences, for pillars, colonnades and floor tiles.
Marbles range in colour from snow-white to grey and black; many varieties have shades of red, yellow, pink, green or buff. The colours, which are caused by the presence of impurities mixed in with the calcite, are frequently arranged in bands or patches which add to the beauty of the stone when it is cut and polished.
Marble was used extensively by the ancient Greeks, for example in the Parthenon, and has been favoured as a sculpting material throughout history, especially during the Renaissance. Michelangelo's famous sculptures ‘David’ and the ‘Venus de’ Medici’ are made of marble.
Among the famous marbles of Italy are the Carrara and Siena marbles of Tuscany.
Some of the marble being used in the Sculptures is from a now disused quarry at Paris Creek in Battunga Country, in South Australia. Famous for its grey and cream marble, Paris Creek marble was used for the State War Memorial on North Terrace in Adelaide. Macclesfield, also in Battunga Country, was an important source of pink marble. Marbles are quarried in all parts of the world. When freshly quarried it is slightly “soft” and a little more flexible, therefore easier to work in finer detail.
Sculptors carving tools are often made of steel or iron which has a general hardness of about 5 (on Moh’s Scale of hardness from 1 – 10), making it easier to carve marble. Those who carve the granite need to use diamond tipped tools.
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At GZ you will find a sculpture. To claim this earthcache please email your answers to the following questions.
Q1: What is the process Limestone goes through to become Marble?
Q2: What colour marble was used for this sculpture?
Q3: Did the artist scribe their name into the piece and if so where?
Q4: (Optional question) Why do you think i called this one Twilight? Hint:- look at the sculpture during sunlight or at night time with a torch.