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Alabaster is a name applied to varieties of two distinct minerals: gypsum (a hydrous sulfate of calcium) and calcite (a carbonate of calcium). The former is the alabaster of the present day; generally, the latter is the alabaster of the ancients.
The two kinds are distinguished from one another readily, because of differences in their relative hardness. The gypsum kind is so soft as to be readily scratched with a fingernail (Mohs hardness 1.5 to 2), while the calcite kind is too hard to be scratched in this way (Mohs hardness 3), although it does yield readily to a knife. Moreover, the calcite alabaster, being a carbonate, effervesces upon being touched with hydrochloric acid, whereas the gypsum alabaster, when thus treated, remains practically unaffected.
Due to the characteristic color of white alabaster, the term has entered the vernacular as a metonym for white things, particularly "alabaster skin", which is very light and quite transparent. This use to imply whiteness occurs in a line from the poem and song, America the Beautiful.
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The origin of the word, alabaster, is in Middle English, through Old French alabastre, in turn derived from the Latin alabaster and that from Greek ἀλάβαστÏος (alabastros) or ἀλάβαστος (alabastos). The latter was a term used to identify a vase made of alabaster.1
This name may derive further from the Ancient Egyptian word a-labaste, which refers to vessels of the Egyptian goddess Bast, who was represented as a lioness and frequently depicted as such when placed atop these alabaster vessels.23 It has been suggested that the name was derived from the town of Alabastron in Egypt, while an Arabic etymological origin also has been suggested.4
This substance, the "alabaster" of the Ancient Egyptians and Bible, often is termed Oriental alabaster, since the early examples came from the Far East. The Greek name alabastrites is said to be derived from the town of Alabastron, in Egypt, where the stone was quarried, but the locality probably owed its name to the mineral; the origin of the mineral name is obscure.
This "Oriental" alabaster was highly esteemed for making small perfume bottles or ointment vases called alabastra, and this has been conjectured to be a possible source of the name. Alabaster also was employed in Egypt for canopic jars and various other sacred and sepulchral objects. A sarcophagus, sculptured in a single block of translucent calcite alabaster from Alabastron, is in the Sir John Soane's Museum, London. This was discovered by Giovanni Belzoni in 1817 in the tomb of Seti I near Thebes. It was purchased by Sir John Soane, previously having been offered to the British Museum.
When cut in thin sheets, alabaster is translucent enough to be used for small windows and has been used for this purpose in medieval churches, especially in Italy. Large alabaster sheets are used extensively in the Cathedral of Our Lady of the Angels, which was dedicated in 2002 by the Los Angeles, California Archdiocese. The cathedral incorporates special cooling to prevent the panes from overheating and turning opaque.
Calcite alabaster 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, whence it is known as onyx-marble or alabaster-onyx, or sometimes simply as onyx — a term that should be restricted to siliceous minerals, however.
Egyptian alabaster has been worked extensively near Suez and Assiut; there also are many ancient quarries in the hills overlooking the plain of Tell el Amarna.
Algerian onyx-marble has been quarried largely in the province of Oran. 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 California, Arizona, Utah, Colorado, and Virginia.
When the term "alabaster" is used without any qualification, it invariably means a fine-grained variety of gypsum. This mineral, or alabaster proper, occurs in England. The early use of alabaster for vessels dedicated for use in the cult of the deity, Bast, in the culture of the Ancient Egyptians is well documented, however, thousands of gypsum alabaster artifacts dating to the late 4th millennium BC also have been found in Tell Brak (present day Nagar), in Syria.5 In Mesopotamia, a gypsum alabaster sculpture, believed to represent the deity, Abu, dates to the first half of the 3rd millennium BC.6
Mineral alabaster 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 fifteenth century its carving into icons and altarpieces was a valuable local industry in Nottingham, as well as a major English export. Beside 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 subordinate 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 form of the gypsum-based mineral. This black form is only found in three veins in the world, one each in Oklahoma (USA), Italy, and the People's Republic of 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.
The finer kinds of alabaster are employed largely as an ornamental stone, especially for ecclesiastical decoration and for the rails of staircases and halls. Its softness enables it to be carved readily into elaborate forms, but its solubility in water renders it unsuitable for outdoor work.
The purest alabaster is a snow-white material of fine tiniforni grain, but it often is associated with an oxide of iron, which produces brown clouding and veining in the stone. The coarser varieties of alabaster are converted by calcination into plaster of Paris, whence they sometimes are known as "plaster stone."
On the continent of Europe, the centre of the alabaster trade is Florence, Italy. Tuscan alabaster occurs in nodular masses embedded in limestone, interstratified with marls of Miocene and Pliocene age. The mineral is worked largely by means of underground galleries, in the district of Volterra. Several varieties are recognized — veined, spotted, clouded, agatiform, and others. The finest kind, obtained principally from Castellina, is sent to Florence for figure-sculpture, while the common kinds are carved locally, at a very cheap rate, into vases, clock-cases, and various ornamental objects. These items are objects of extensive trade, especially in Florence, Pisa, and Livorno.
In order to diminish the translucency of the alabaster and to produce an opacity suggestive of true marble, the statues are immersed in a bath of water and heated gradually — nearly to the boiling-point — an operation requiring great care, for if the temperature is not regulated carefully, the stone acquires a dead-white, chalky appearance. The effect of heating appears to be a partial dehydration of the gypsum. If properly treated, it very closely resembles true marble and is known as marmo di Castellina.
Sulphate of lime (gypsum) also was used by the ancients. It was employed, for instance, in Assyrian sculpture. So some of the ancient alabaster is identical to the modern stone.
Alabaster may be stained to disguise it, by being heated in various pigmentary solutions. In this way a very misleading imitation of coral has been produced, that is called (alabaster coral).
J. A. Harrell, "Misuse of the term 'alabaster' in Egyptology," Göttinger Miszellen, v. 119, 1990, pp. 37–42.
Tim Mackintosh-Smith, "Moonglow from Underground". Aramco World May-June 1999.[1]
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This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.
The above article is licensed under the GNU Free Documentation License. It uses material from the copyrighted Wikipedia "Alabaster" article.