Marble Idols - Agra
Marble is a distinctive type of stone made naturally occurred from limestone. Marble as a medium to sculpt statues is appreciated by many great sculptors. Marble is derived from the Latin word ‘Marmar’, which has come from the Greek word “Marmarous” meaning the shining stone. Marble locally in northern India is known as Sangemarmar. The main constituents of marble are calcium and dolomite. The hardness of marble ranges from 2.5 to 5 on the Moh’s.
a. Dolomite: If it has more than 40% magnesium carbonate.
b. Magnesium: If it has between 5% and 40% magnesium.
c. Calcite: If it has less than 5% magnesium carbonate.
In the earth's crust, marbles can be found interblended with metamorphic rocks like phyllites, mica schists, granulites etc. which are in the older layers of the earth’s crust and formed due to extreme folding and igneous incursion, in the region of Makrana (Rajasthan) the change of limestone’s rich fossils are turned into true marble, which is a common phenomenon in such metamorphic region. White and gray marble which are found in different parts of India and also abroad are in the recrystallized rock form. Many of these places have been quarried for 1000s of years and are still in use. Legendary sculptors like Michelangelo and Antonio Canova have used marble from these regions to sculpt extraordinary statues. The purest form of marble also consists of an impurity such as small rounded grains, dark shining flakes of graphite, iron oxides, colorless pale yellow mica and silicate of lime and magnesia. Many of the minerals, semi-precious and gems like biotite, talc, zoisite, chlorite, forsterite, garnet, titanite, spinel, vesuvianite, and tourmaline are found in the same layer where marble is found. Due to the presence of silicate minerals different colors of marbles are obtained. Green color marble is obtained due to the presence of green pyroxenes and amphiboles, brown from garnet and vesuvianite, yellow color from epidote, chondrodite and titanite, black and grey color from graphite present in marbles. Sometimes interesting patterns may be seen on the marble, when calc-silicate rock bonds with marble and forms nodules and patches, marble statues with calc-silicate bonds are hard to finish because of the variation in the hardness between the layers of marble.
The extraction of marble from the mine is done with a limited amount of explosion because usage of too much explosion may shatter the rock. Large channelling machines are used to cut a deep slice into the marble which is about 2 to 3 inches wide, due to the natural cracks present in the marble stone, it is easy to spill into the required size. The large size marble is fed into the sawmills, where they are cut into required size slabs, sets of parallel iron blades cut through marble which moves back and forth, and a mixture of sand and water is fed to the blade to ease the cutting process. The marble stone is machined with carborundum wheels for a smooth surface and finer grades of abrasive are used for polishing. Throughout the process, even with most high-tech machinery, about 50 % of the stone is wasted. Small chunks of marble are used in terrazzo flooring and stucco wall finish.
Identification of marble from other contemporary stones:
1. To identify the stone, make sure its surface is free from grime, dirt and debris by washing it, these impurities may affect the identification process.
2. Marbles are very smooth and silky and this can be checked by touching the surface of it. If there is any roughness on the surface, then the stone is not a pure marble.
3. Looking at the material from different angles should give out a glossy and almost translucent effect. Marbles are highly reflective and shiny once polished.
4. Looking at the patterns on the marble gives an idea about the purity of stone. Grains, which run through the marble, are fluid lines that create an unsystematic pattern, swirl and smudge of lines. If the stone has crystal like markings and speckles are seen, then the stone is likely to be granite.
5. 100 % pure marble is available in very limited colors, like white, black, grey, cream and red. If marbles are available in colors like bright green, pink and yellow, it is said that the stone contains impurities.
6. Marbles are heavy compared to their contemporary. By lifting a small piece of marble, the heaviness can be felt. Many times granite is also found as heavy as marble but the identification can be done with the help of textures and patterns.
7. Marbles do not absorb water, so by splashing water on its surface. If the water seeps in, then the stone is not marble.
8. Using a pocket knife to scratch the surface of the marble, there should be no or very less marks seen on the surface. If a deep cut can be seen, then it’s not marble.
9. Mable statues generally craved out of single pieces, so the base would be always solid and not hollow.
10. By examining the marble with a magnifying glass, if the core is easily visible with fewer marks, it is valued at a higher price.
11. Brightness of color and symmetry of design also pay’s higher price.
