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Alabaster is one of the most distinctive and very famous and artistic stones for ancient and contemporary sculptors and architects, who are interested in it and have the ability to benefit from its features and technical characteristics. It is one of the wonderful stones of outstanding beauty. It is worth noting that alabaster is not included in precious or semi-precious stones. As for the name alabaster, it was given the name of a village in ancient Egypt that was located near the city of Thebes, where transparent limestone was extracted from it. And eventually the term alabaster began to be applied only to the translucent white rocks used in art. It is also now called a wide variety of transparent gypsum which has very low porosity and appears in very light colours.
Learn about alabaster
alabaster stone is formed From microcrystalline gypsum groups of sizes ranging 10-80 micrometers, which form an irregular mosaic shape. The groups of the finest grain size stones are the best quality among the alabaster stones and the majority of them are translucent. The impurities between these groups of clay and the salts that accumulate with gypsum are known and can determine the color and pattern of the stone.
Alabaster extraction sites
Deposits of alabaster stones were found in Many countries of the world such as Britain, Belgium, India, Turkey, Cyprus, USA, Italy and Spain. The veins of alabaster extracted from open pits were also found at a depth of up to 16-20 feet below the surface of the earth. As for the size, the length is usually 20-200 feet, and from two to three feet in diameter. And very rare species of alabaster exceed this size. The alabaster stones are transported from the quarry to a plant for dissemination, where they are cut into flat, flat shapes of different sizes.
Alabaster formation
Alabaster is a gypsum stone. It is known that gypsum is a salt formed by rain in lakes and ponds that are exposed to intense evaporation. (Evaporative ponds). When the water mass decreases, the degree of saturation needed by the different salts for precipitation is reached. The accumulation of small gypsum crystals at the bottom of the lakes leads to a process that eventually leads to the formation of alabaster stones. The gypsum deposits at the bottom of the lake are gradually buried under new sedimentary material. This leads to a change in pressure and temperature conditions, which benefits the loss of water molecules in these small crystals, and thus turns gypsum into anhydrite, which is more stable in such environmental conditions. It is estimated that these changes occur at a depth of about 285 meters. This process involves a shortage of approximately 285% in volume The first is due to both water loss and structural reorganization.
If environmental conditions change again (due to terrain elevation and erosion), pressure and temperature drop in the presence of water, a reverse mineralization process can occur in the crystal structure Meaning that the water molecules are recovered along with the conversion of anhydrite to gypsum. Two extreme forms of the crystallization process will be produced depending on how the process develops. If the water is recovered slowly, there will be enough time for well-developed crystals of specific shapes and large sizes to form. However, under conditions of rapid drying, large crystals will not have time to form, so the growing crystals are bound together to provide a stable microcrystalline framework which means alabaster.
Alabaster stone is used in the manufacture of various types of sculptures
Characteristics of alabaster stone
The alabaster stone has a crystal size (less than 0.242 mm) that appears in a basic frame that would add transparency and compactness to the stone. It is characterized by several other wonderful qualities, and the first of these qualities is its distinctive beauty. The second characteristic is its low degree of hardness, and this characteristic makes the stone very valuable. On the other hand, alabaster stone easily stains with iron oxides.
However, alabaster stone also has disadvantages in that, due to its susceptibility to the loss of water molecules, it is possible to modify the mineral composition partially or completely of a sample of those Stones when heat is applied (alabaster begins to decompose at º 285º) or when These samples are subjected to special conditions of humidity. It should also be kept in mind that alabaster is a water-soluble salt, which results in a restriction of use depending on the environmental conditions to which the stone will be exposed.
Alabaster stones are usually found in spherical pieces. Its diameter reaches one mm. As a result, professional diamond suppliers use the following two terms:
“Boulder”: It is a rough stone that is extracted from quarries and cleaned of clay and does not undergo any modifications.
Veins are coloured streaks that differ from the hue of the stone’s base. These veins, in general, are caused by the presence of clay inclusions and do not include any holes in the stone.
Because of the size of the minuscule crystals, a more or less translucent pattern with the base colour of the stone may form. Furthermore, there are no holes in the stone.
