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Marble is a metamorphic rock derived from limestone, composed mostly of calcite (a crystalline form of calcium carbonate, CaCO3). The original source of the parent limestone is the seabed deposition in the form of microscopic animal skeletons or similar materials. Marble is formed when the limestone is transformed by heat and pressure after being overlain by other materials. The finest marbles for sculpture have no or few stains (some natural stain can be seen in the sculpture shown at left, which the sculptor has skillfully incorporated into the sculpture). Among the commonly available stones only marble has a slight surface translucency that is comparable to that of human skin. It is this translucency that gives a marble sculpture a visual depth beyond its surface and this evokes a certain realism when used for figurative works. Marble also has the advantage that when first quarried it is relatively soft and easy to work, refine, and polish. As the finished marble ages it becomes harder and more durable. Preference to the cheaper and less translucent limestone is based largely on the fineness of marble's grain, which enables the sculptor to render minute detail in a manner not always possible with limestone; it is also more weather resistant. Marble does not bear handling well as it will absorb skin oils when touched, which leads to yellow brownish staining. While more resistant than limestone it is subject to attack by weak acids, and so performs poorly in outdoor environments subject to acid rain. For severe environments, granite is a more lasting material but one which is far more difficult to work and much less suitable for refined works. Compared to metals such as bronze, marble lacks ductility and strength, requiring special structural considerations when planning a sculpture. In the sculpture shown to the right, the figure can be placed upon slender lower legs and the balls of the feet only because the bending stress in the sculpture is taken through the flowing drapery of the skirt, which is founded upon an upthrust portion of the ground and with the feet forms a tripod-like foundation for the mass. For comparison see some of the examples in the article concerning bronze sculpture (especially the sculpture) for the ease with which action and extension may be expressed. The final stage of the carving process is polishing. Sandpaper can be used as a first step in the polishing process, or sand cloth. Emery, a stone that is harder and rougher than the sculpture media, is also used in the finishing process. This abrading, or wearing away, brings out the color of the stone, reveals patterns in the surface and adds a sheen. Tin and iron oxides are often used to give the stone a highly reflective exterior. In short, as a global business E-platform of promoting stone industry, so far, So far, our client resource has accounted over 100 thousand spreading more than 100 countries and regions, with a visit volume exceeding 5 million times annually. If you want to consult us freely, you can also see qurries or become an honest follower of us by @stonebtb of https://twitter.com.
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