Алабастр тасы: қасиеттері, қолданылуы және тарихы

Lightly colored, translucent, and soft calcium minerals, typically gypsum

Alabaster is a mineral and a soft rock used for carvings and as a source of plaster powder. Archaeologists, geologists, and the stone industry have different definitions and usages for the word alabaster. In archaeology, the term alabaster is a category of objects and artefacts made from the varieties of two different minerals: (i) the fine grained, massive type of gypsum, and (ii) the fine grained, banded type of calcite. Chemically, gypsum is a hydrous sulfate of calcium, whereas calcite is a carbonate of calcium. Calcite alabaster also is known as: onyx marble, Egyptian alabaster, and Oriental alabaster, which terms usually describe either a compact, banded travertine stone

The English word "alabaster" was borrowed from Old French alabastre, in turn derived from Latin alabaster, and that from Greek ἀλάβαστρος (alábastros) or ἀλάβαστος (alábastos). The Greek words denoted a vase of alabaster. The name may be derived further from ancient Egyptian a labaste, which refers to vessels of the Egyptian goddess Bast. She was represented as a lioness and frequently depicted as such in figures placed atop these alabaster vessels. Ancient Roman authors Pliny the Elder and Ptolemy wrote that the stone used for ointment jars called alabastra came from a region of Egypt known as Alabastron or Alabastrites.

The purest alabaster is a snow white material of fine uniform grain, but it often is associated with an oxide of iron, which produces brown clouding and veining in the stone. The coarser varieties of gypsum alabaster are converted by calcination into plaster of Paris, and are sometimes known as "plaster stone". The finer kinds of alabaster are employed largely as an ornamental stone, especially for ecclesiastical decoration and for the rails of staircases and halls.

Alabaster is mined and then sold in blocks to alabaster workshops. There they are cut to the needed size ("squaring"), and then are processed in different techniques: turned on a lathe for round shapes, carved into three dimensional sculptures, chiselled to produce low relief figures or decoration; and then given an elaborate finish that reveals its transparency, colour, and texture. For this the stone needs to be fully immersed in various pigmentary solutions and heated to a specific temperature.

When cut in thin sheets, alabaster is translucent enough to be used for small windows. It was used for this purpose in Byzantine churches and later in medieval ones, especially in Italy. Large sheets of Aragonese gypsum alabaster are used extensively in the contemporary Cathedral of Our Lady of the Angels, The cathedral incorporates special cooling to prevent the panes from overheating and turning opaque. while the modern Los Angeles cathedral is using gypsum alabaster. There are also multiple examples of alabaster windows in ordinary village churches and monasteries in northern Spain.

Calcite alabaster, harder than the gypsum variety, was the kind primarily used in ancient Egypt and the wider Middle East (but not Assyrian palace reliefs), and is also used in modern times. It is found as either a stalagmitic deposit from the floor and walls of limestone caverns, or as a kind of travertine, similarly deposited in springs of calcareous water. Its deposition in successive layers gives rise to the banded appearance that the marble often shows on cross section, from which its name is derived: onyx marble or alabaster onyx, or sometimes simply (and wrongly) as onyx.

In Mexico, there are famous deposits of a delicate green variety at La Pedrara, in the district of Tecali, near Puebla. Onyx marble occurs also in the district of Tehuacán and at several localities in the US including California, Arizona, Utah, Colorado and Virginia. In Mesopotamia, gypsum alabaster was the material of choice for figures of deities and devotees in temples, as in a figure believed to represent the deity Abu dating to the first half of the 3rd millennium BC and currently kept in New York.

Much of the world's alabaster extraction is performed in the centre of the Ebro Valley in Aragon, Spain, which has the world's largest known exploitable deposits. According to a brochure published by the Aragon government, alabaster has elsewhere either been depleted, or its extraction is so difficult that it has almost been abandoned or is carried out at a very high cost. During the Middle Ages the craft of alabaster was almost completely forgotten. In the 17th and 18th centuries production of artistic, high quality Renaissance style artifacts stopped altogether, being replaced by less sophisticated, cheaper items better suited for large scale production and commerce. The new industry prospered, but the reduced need of skilled craftsmen left only few still working. The 19th century brought a boom to the industry, largely due to the "traveling artisans" who went and offered their wares to the palaces of Europe, as well as to America and the East.

Gypsum alabaster is a common mineral, which occurs in England in the Keuper marls of the Midlands, especially at Chellaston in Derbyshire, at Fauld in Staffordshire, and near Newark in Nottinghamshire. Deposits at all of these localities have been worked extensively. In the 14th and 15th centuries its carving into small statues and sets of relief panels for altarpieces was a valuable local industry in Nottingham, as well as a major English export. These were usually painted, or partly painted. It was also used for the effigies, often life size, on tomb monuments, as the typical recumbent position suited the material's lack of strength, and it was cheaper and easier to work than good marble. After the English Reformation the making of altarpiece sets was discontinued, but funerary monument work in reliefs and statues continued. Besides examples of these carvings still in Britain (especially at the Nottingham Castle Museum, British Museum, and Victoria and Albert Museum), trade in mineral alabaster (rather than just the antiques trade) has scattered examples in the material that may be found as far afield as the Musée de Cluny, Spain, and Scandinavia. Alabaster also is found, although in smaller quantity, at Watchet in Somerset, near Penarth in Glamorganshire, and elsewhere. In Cumbria it occurs largely in the New Red rocks, but at a lower geological horizon. The alabaster of Nottinghamshire and Derbyshire is found in thick nodular beds or "floors" in spheroidal masses known as "balls" or "bowls" and in smaller lenticular masses termed "cakes". At Chellaston, where the local alabaster is known as "Patrick", it has been worked into ornaments under the name of "Derbyshire spar"―a term more properly applied to fluorspar.

Black alabaster is a rare anhydrite form of the gypsum based mineral. This black form is found in only three veins in the world, one each in United States, Italy, and China. Alabaster Caverns State Park, near Freedom, Oklahoma, is home to a natural gypsum cave in which much of the gypsum is in the form of alabaster. There are several types of alabaster found at the site, including pink, white, and the rare black alabaster.