Alabaster - AbsoluteAstronomy.com

Alabaster is a name applied to varieties of two distinct mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

s, when used as a material: gypsum

Gypsum

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

(a hydrous

Hydroxyl

A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...

sulfate

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

of calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

) and calcite

Calcite

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

(a carbonate

Carbonate

In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

of calcium). The former is the alabaster of the present day; generally, the latter is the alabaster of the ancients. Both are easy to work, with an attractive appearance, and have been used for making a variety of artworks and objects, especially small carvings.

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

Mohs scale of mineral hardness

The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...

1.5 to 2), while the calcite kind is too hard to be scratched in this way (Mohs hardness

Mohs scale of mineral hardness

3), although it does yield readily to a knife. Moreover, the calcite alabaster, being a carbonate

Carbonate

, effervesces

Effervescence

Effervescence might refer to one of the following:*Effervescence is the escape of gas from an aqueous solution.*Collective effervescence is a perceived energy formed by a gathering of people....

upon being touched with hydrochloric acid

Hydrochloric acid

Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric 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

Metonymy

Metonymy is a figure of speech used in rhetoric in which a thing or concept is not called by its own name, but by the name of something intimately associated with that thing or concept...

for white

White

White is a color, the perception of which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in nearly equal amounts and with high brightness compared to the surroundings. A white visual stimulation will be void of hue and grayness.White light can be...

things, particularly "alabaster skin", which means very light and quite transparent, and no doubt derives from the use of alabaster for tomb effigies.

Etymology

The origin of the word, alabaster, is in Middle English, through Old French alabastre, in turn derived from the Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

alabaster and that from Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

ἀλάβαστρος (alabastros) or ἀλάβαστος (alabastos). The latter was a term used to identify a vase made of alabaster.

This name may derive further from the Ancient Egypt

Ancient Egypt

Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

ian word 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. Other suggestions include derivation from the town of Alabastron

Alabastron

An alabastron is a type of pottery used in the ancient world for holding oil, especially perfume or massage oils...

in Egypt.

Calcite alabaster

This substance, the "alabaster" of the Ancient Egyptians and Bible

Bible

The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

, often is termed Oriental alabaster, since the early examples came from the Far East

Far East

The Far East is an English term mostly describing East Asia and Southeast Asia, with South Asia sometimes also included for economic and cultural reasons.The term came into use in European geopolitical discourse in the 19th century,...

. The Greek

Greek language

name alabastrites is said to be derived from the town of Alabastron, in Egypt

Egypt

Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

, where the stone was quarried. The locality probably owed its name to the mineral; the origin of the mineral name is obscure.

The "Oriental" alabaster was highly esteemed for making small perfume bottles or ointment vases called alabastra

Alabastron

An alabastron is a type of pottery used in the ancient world for holding oil, especially perfume or massage oils...

, the vessel name has been suggested as a possible source of the mineral name. In Egypt craftsmen used alabaster for canopic jar

Canopic jar

Canopic jars were used by the Ancient Egyptians during the mummification process to store and preserve the viscera of their owner for the afterlife. They were commonly either carved from limestone or were made of pottery...

s and various other sacred and sepulchral objects. A sarcophagus

Sarcophagus

A sarcophagus is a funeral receptacle for a corpse, most commonly carved or cut from stone. The word "sarcophagus" comes from the Greek σαρξ sarx meaning "flesh", and φαγειν phagein meaning "to eat", hence sarkophagus means "flesh-eating"; from the phrase lithos sarkophagos...

, sculptured in a single block of translucent calcite alabaster from Alabastron, is in the Sir John Soane's Museum, London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

. This was discovered by Giovanni Belzoni in 1817 in the tomb of Seti I

Seti I

Menmaatre Seti I was a Pharaoh of Ancient Egypt , the son of Ramesses I and Queen Sitre, and the father of Ramesses II...

near Thebes

Thebes, Egypt

Thebes is the Greek name for a city in Ancient Egypt located about 800 km south of the Mediterranean, on the east bank of the river Nile within the modern city of Luxor. The Theban Necropolis is situated nearby on the west bank of the Nile.-History:...

. It was purchased by Sir John Soane

John Soane

Sir John Soane, RA was an English architect who specialised in the Neo-Classical style. His architectural works are distinguished by their clean lines, massing of simple form, decisive detailing, careful proportions and skilful use of light sources...

.

When cut in thin sheets, alabaster is translucent enough to be used for small windows. It was used for this purpose in medieval churches, especially in Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. Large alabaster sheets are used extensively in the contemporary Cathedral of Our Lady of the Angels

Cathedral of Our Lady of the Angels

The Cathedral of Our Lady of the Angels, also called "COLA" and the Los Angeles Cathedral, is a cathedral of the Roman Catholic Church in Los Angeles, California, United States...

, 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

Stalagmite

A stalagmite is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. This stalagmite formation occurs only under certain pH conditions within the underground cavern. The corresponding formation on...

deposit, from the floor and walls of limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

caverns, or as a kind of travertine

Travertine

Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, and cream-colored varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot...

, 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

Onyx

Onyx is a banded variety of chalcedony. The colors of its bands range from white to almost every color . Commonly, specimens of onyx contain bands of black and/or white.-Etymology:...

. The latter term should be restricted to siliceous minerals, however.

Egyptian alabaster has been worked extensively near Suez

Suez

Suez is a seaport city in north-eastern Egypt, located on the north coast of the Gulf of Suez , near the southern terminus of the Suez Canal, having the same boundaries as Suez governorate. It has three harbors, Adabya, Ain Sokhna and Port Tawfiq, and extensive port facilities...

and Assiut. Many ancient quarries are found in the hills overlooking the plain of Tell el Amarna.

Algeria

Algeria

Algeria , officially the People's Democratic Republic of Algeria , also formally referred to as the Democratic and Popular Republic of Algeria, is a country in the Maghreb region of Northwest Africa with Algiers as its capital.In terms of land area, it is the largest country in Africa and the Arab...

n onyx-marble has been quarried largely in the province of Oran

Oran

Oran is a major city on the northwestern Mediterranean coast of Algeria, and the second largest city of the country.It is the capital of the Oran Province . The city has a population of 759,645 , while the metropolitan area has a population of approximately 1,500,000, making it the second largest...

. In Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, there are famous deposits of a delicate green variety at La Pedrara, in the district of Tecali, near Puebla

Puebla, Puebla

The city and municipality of Puebla is the capital of the state of Puebla, and one of the five most important colonial cities in Mexico. Being a planned city, it is located to the east of Mexico City and west of Mexico's main port, Veracruz, on the main route between the two.The city was founded...

. Onyx-marble occurs also in the district of Tehuacán

Tehuacán

Tehuacán is the second largest city in the Mexican state of Puebla, nestled in the Southeast Valley of Tehuacán, bordering the states of Oaxaca and Veracruz. The 2010 census reported a population of 248,716 in the city and 274,906 in its surrounding municipality of the same name, of which it serves...

and at several localities in California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

, Utah

Utah

Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

, and Virginia

Virginia

The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

Gypsum alabaster

When the term "alabaster" is used without any qualification, it invariably means a fine-grained

Granularity

Granularity is the extent to which a system is broken down into small parts, either the system itself or its description or observation. It is the "extent to which a larger entity is subdivided...

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

Artifact (archaeology)

An artifact or artefact is "something made or given shape by man, such as a tool or a work of art, esp an object of archaeological interest"...

dating to the late 4th millennium BC

4th millennium BC

The 4th millennium BC saw major changes in human culture. It marked the beginning of the Bronze Age and of writing.The city states of Sumer and the kingdom of Egypt were established and grew to prominence. Agriculture spread widely across Eurasia...

also have been found in Tell Brak (present day Nagar

Nagar, Syria

Tell Brak, ancient Nagar, is a tell, or settlement mound, in the Upper Khabur area in Al-Hasakah Governorate, northeastern Syria. The site was occupied between the sixth and second millennia BCE...

), in Syria

Syria

Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....

. In Mesopotamia

Mesopotamia

Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...

, a gypsum alabaster sculpture

Sculpture

Sculpture is three-dimensional artwork created by shaping or combining hard materials—typically stone such as marble—or metal, glass, or wood. Softer materials can also be used, such as clay, textiles, plastics, polymers and softer metals...

, believed to represent the deity, Abu

Abu (god)

Abu in Sumerian mythology was a minor god of plants. He was one of the eight deities born to relieve the illness of Enki....

, dates to the first half of the 3rd millennium BC

3rd millennium BC

The 3rd millennium BC spans the Early to Middle Bronze Age.It represents a period of time in which imperialism, or the desire to conquer, grew to prominence, in the city states of the Middle East, but also throughout Eurasia, with Indo-European expansion to Anatolia, Europe and Central Asia. The...

.

Gypsum alabaster is a common mineral, which occurs in England in the Keuper

Keuper

The Keuper is a lithostratigraphic unit in the subsurface of large parts of west and central Europe. The Keuper consists of dolostone, shales or claystones and evaporites that were deposited during the Middle and Late Triassic epochs...

marl

Marl

Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay...

s of the Midlands

English Midlands

The Midlands, or the English Midlands, is the traditional name for the area comprising central England that broadly corresponds to the early medieval Kingdom of Mercia. It borders Southern England, Northern England, East Anglia and Wales. Its largest city is Birmingham, and it was an important...

, especially at Chellaston

Chellaston

Chellaston is a suburb of the City of Derby, which is in the East Midlands in England in the United Kingdom. It is on a natural hill, and has recently expanded due to several new housing estates....

in Derbyshire

Derbyshire

Derbyshire is a county in the East Midlands of England. A substantial portion of the Peak District National Park lies within Derbyshire. The northern part of Derbyshire overlaps with the Pennines, a famous chain of hills and mountains. The county contains within its boundary of approx...

, at Fauld in Staffordshire

Staffordshire

Staffordshire is a landlocked county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. Part of the National Forest lies within its borders...

, and near Newark in Nottinghamshire

Nottinghamshire

Nottinghamshire is a county in the East Midlands of England, bordering South Yorkshire to the north-west, Lincolnshire to the east, Leicestershire to the south, and Derbyshire to the west...

. Deposits at all of these localities have been worked extensively. In the fifteenth century its carving into small statues and sets of relief

Relief

Relief is a sculptural technique. The term relief is from the Latin verb levo, to raise. To create a sculpture in relief is thus to give the impression that the sculpted material has been raised above the background plane...

panels for altarpiece

Altarpiece

An altarpiece is a picture or relief representing a religious subject and suspended in a frame behind the altar of a church. The altarpiece is often made up of two or more separate panels created using a technique known as panel painting. It is then called a diptych, triptych or polyptych for two,...

s was a valuable local industry in Nottingham

Nottingham Alabaster

Nottingham alabaster is a term used to refer to the English sculpture industry, mostly of relatively small religious carvings, which flourished from the fourteenth century until the early sixteenth century...

, 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. Beside examples of these carvings still in Britain (especially at the Nottingham Castle Museum, British Museum

British Museum

The British Museum is a museum of human history and culture in London. Its collections, which number more than seven million objects, are amongst the largest and most comprehensive in the world and originate from all continents, illustrating and documenting the story of human culture from its...

, and Victoria and Albert Museum

Victoria and Albert Museum

The Victoria and Albert Museum , set in the Brompton district of The Royal Borough of Kensington and Chelsea, London, England, is the world's largest museum of decorative arts and design, housing a permanent collection of over 4.5 million objects...

), 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

Musée de Cluny

The Musée de Cluny , officially known as Musée National du Moyen Âge , is a museum in Paris, France...

, Spain, and Scandinavia.

Alabaster also is found, although in smaller quantity, at Watchet

Watchet

Watchet is a harbour town and civil parish in the English county of Somerset, with an approximate population of 4,400. It is situated west of Bridgwater, north-west of Taunton, and east of Minehead. The parish includes the hamlet of Beggearn Huish...

in Somerset

Somerset

The ceremonial and non-metropolitan county of Somerset in South West England borders Bristol and Gloucestershire to the north, Wiltshire to the east, Dorset to the south-east, and Devon to the south-west. It is partly bounded to the north and west by the Bristol Channel and the estuary of the...

, near Penarth

Penarth

Penarth is a town and seaside resort in the Vale of Glamorgan , Wales, 5.2 miles south west from the city centre of the Welsh capital city of Cardiff and lying on the north shore of the Severn Estuary at the southern end of Cardiff Bay...

in Glamorganshire, and elsewhere. In Cumbria

Cumbria

Cumbria , is a non-metropolitan county in North West England. The county and Cumbria County Council, its local authority, came into existence in 1974 after the passage of the Local Government Act 1972. Cumbria's largest settlement and county town is Carlisle. It consists of six districts, and in...

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.

In Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, the centre of the alabaster trade today is Florence, Italy. Tuscan

Tuscany

Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence ....

alabaster occurs in nodular masses embedded in limestone, interstratified with marl

Marl

s of Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

and Pliocene

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

age. The mineral is worked largely by means of underground galleries, in the district of Volterra

Volterra

Volterra, known to the ancient Etruscans as Velathri, to the Romans as Volaterrae, is a town and comune in the Tuscany region of Italy.-History:...

. Several varieties are recognized—veined, spotted, clouded, agatiform, and others. The finest kind, obtained principally from Castellina

Castellina Marittima

Castellina Marittima is a comune in the province of Pisa in the Italian region Tuscany, located about 70 km southwest of Florence and about 35 km southeast of Pisa....

, is sent to Florence for figure-sculpture, while the common kinds are carved locally, into vases, lights, and various ornamental objects. These items are objects of extensive trade, especially in Florence, Pisa

Pisa

Pisa is a city in Tuscany, Central Italy, on the right bank of the mouth of the River Arno on the Tyrrhenian Sea. It is the capital city of the Province of Pisa...

, and Livorno

Livorno

Livorno , traditionally Leghorn , is a port city on the Tyrrhenian Sea on the western edge of Tuscany, Italy. It is the capital of the Province of Livorno, having a population of approximately 160,000 residents in 2009.- History :...

. Spain and many other countries have deposits which have been worked.

Black alabaster

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

Oklahoma

Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

, Italy

Italy

, and China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

.

Alabaster Caverns State Park

Alabaster Caverns State Park

Alabaster Caverns State Park, near Freedom, Oklahoma is a state park and home to the largest natural gypsum cave in the world that is open to the public. The gypsum is mostly in the form of alabaster. There are several types of alabaster found at the site, including pink, white, and the rare...

, near Freedom, Oklahoma

Freedom, Oklahoma

Freedom is a town in Woods County, Oklahoma, United States. The population was 289 at the 2010 census.-Geography:Freedom is located at .According to the United States Census Bureau, the town has a total area of , all of it land.-Climate:...

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.

Uses

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. If alabaster with a smooth, polished surface is washed with washing-up liquid (dishwashing liquid), it will become rough, dull and whiter, losing most of its translucency and lustre.

The purest alabaster is a snow-white material of fine tiniforni grain, but it often is associated with an oxide of iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

, 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."

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

Coral (precious)

Precious coral or red coral is the common name given to Corallium rubrum and several related species of marine coral. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink skeleton, which is used for making jewelry.-Habitat:Red corals grow on rocky...

that is called alabaster coral is produced.

External links

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