GYPSUM  , a See also:

• COMMON

common See also:

• MINERAL

mineral consisting of hydrous See also:

• CALCIUM [symbol Ca, atomic weight 40.0 (o= x6)]

calcium sulphate, named from the Gr. yb 'os, a word used by See also:

• THEOPHRASTUS

Theophrastus to denote not only the raw mineral but also the See also:

• PRO

pro-duct of its calcination, which was employed in See also:

• ANCIENT
• ANCIENT (also spelt ANTIENT; derived, through the Fr. ancien, old, from the late Lat. antianum, from ante, before)

ancient times, as it still is, as a See also:

• PLASTER

plaster . When crystallized, gypsum is often called selenite, the cre rIYLT c of Dioscorides, so named from aeX$v1i, " the See also:

• MOON (a common Teutonic word, cf. Ger. Mond, Du. maan, Dan. maane, &c., and cognate with such Indo-Germanic forms as Gr. µlip, Sans. ma's, Irish mi, &c.; Lat. uses luna, i.e. lucna, the shining one, lucere, to shine, for the moon, but preserves the word i
• MOON, SIR RICHARD, 1ST BARONET (1814-1899)

moon," probably in allusion to the soft moon-like reflection of See also:

• LIGHT

light from some of its faces, or, according to a See also:

• LEGEND (through the French from the med. Lat. legenda, things to be read, from legere, to read)

legend,. because it is found at See also:

• NIGHT

night when the moon is on the increase . The granular, See also:

• MARBLE (from Lat. marmor, Gr. pApµapos, shining stone)

marble-like gypsum is termed See also:

• ALABASTER
• ALABASTER, or ARBLASTIER, WILLIAM (1567-1640)

alabaster (q.v.) . Gypsum crystallizes in the See also:

• MONOCLINIC

monoclinic See also:

• SYSTEM

system, the See also:

• HABIT (through the French from Lat. habitus, from habere, to have, hold, or, in a reflective sense, to be in a certain condition; in many of the English senses the French use habitude, not habit)

habit of the crystals being usually either prismatic or See also:

• TABULAR

tabular; in the latter See also:

• CASE
• CASE, JOHN (d. 1600)

case the broad planes are parallel to the faces of the clinopinacoid . The crystals may become lenticular by curvature of certain faces . In the characteristic type represented in fig . 1, f represents the See also:

• PRISM (Gr. rrpivµa, properly a thing sawn, Irpii"ety, to saw)

prism, 1 the hemi-See also:

• PYRAMID

pyramid and P the clinopinacoid . Twins are common, as in fig . 2, forming in some cases arrow-headed and See also:

• SWALLOW (A. S. swalewe, Icel. svala, Du. zwaluw, Ger. Schwalbe)

swallow-tailed crystals . Cleavage is perfect parallel to the clinopinacoid, yielding thin plates, often See also:

• DIAMOND

diamond-shaped, with pearly lustre; these flakes are usually flexible, but may be brittle, as in the gypsum of Montmartre . Two other cleavages are recognized, but they are imperfect . Crystals of gypsum, when occurring in See also:

• CLAY (from O. Eng. claeg, a word common in various forms to Teutonic languages, cf. Ger. Klei)
• CLAY, CASSIUS MARCELLUS (1810-1903)
• CLAY, CHARLES (1801–1893)
• CLAY, FREDERIC (1838–1889)
• CLAY, HENRY (1777–1852)

clay, may enclose much muddy See also:

• MATTER

matter; in other cases a large proportion of See also:

• SAND
• SAND, GEORGE (1804-1876)

sand may be mechanically entangled in the crystals without serious disturbance of See also:

• FORM (Lat. forma)

form; whilst certain crystals occasionally enclose cavities with liquid and an See also:

• AIR (from an Indo-European root meaning " breathe," " blow ")
• AIR, or ASBEN

air-bubble .

Gypsum not infrequently becomes fibrous . This variety occurs in See also:

• VEINS

veins, often See also:

• RUNNING

running through gypseous marls, with the See also:

• FIBRES
• FIBRES (or FIBERS, in American spelling; from Lat. fibra, apparently connected either with filum, thread, or findere, to split)

fibres disposed at right angles to the direction of the vein . Such gypsum when cut and polished has a pearly opalescence, or satiny sheen, whence it is called satin-spar (q.v.) . Gypsum is so soft as to be scratched even by the See also:

• FINGER

finger-See also:

• NAIL (O. Eng. naegal, cf. Dutch, Ger., Swed. nagel; the word is also related to Lat. unguis, Gr. ovu, Sans. nakhas)

nail (H= 5 to 2) . Its specific gravity is about 2.3 . The mineral is slightly soluble in See also:

• WATER

water, one See also:

• PART

part of gypsum being soluble, according to G . K . See also:

• CAMERON, JOHN (1579–1623)
• CAMERON, RICHARD (1648?–168o)
• CAMERON, SIMON (1799-1889)
• CAMERON, VERNEY LOVETT (1844–1894)

Cameron, in 372 parts of pure water at 26' C . See also:

• WATERS, TERRITORIAL

Waters percolating through gypseous strata, like the See also:

• KEUPER

Keuper marls, dissolve the calcium sulphate and thus become permanently hard or " selenitic." Such water has See also:

• SPECIAL

special value for See also:

• BREWING

brewing See also:

• PALE (through Fr. pal, from Lat. palms, a stake, for paglus, from the stem pag- of pangere, to fix; " pole " is from the same original source)

pale See also:

• ALE

ale, and the water used by the See also:

• BURTON, JOHN HILL (1809–1881)
• BURTON, ROBERT (1577-1640)
• BURTON, SIR FREDERICK WILLIAM (1816–f goo)
• BURTON, SIR RICHARD FRANCIS (1821-1890)
• BURTON, WILLIAM EVANS (1804-1860)

Burton breweries is of this See also:

• CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character; hence the artificial dissolving of gypsum in water for brewing purposes is known as " burtonization." Deposits of gypsum are formed in boilers using selenitic water . Pure gypsum is colourless or See also:

• WHITE
• WHITE, ANDREW DICKSON (1832– )
• WHITE, GILBERT (1720–1793)
• WHITE, HENRY KIRKE (1785-1806)
• WHITE, HUGH LAWSON (1773-1840)
• WHITE, JOSEPH BLANCO (1775-1841)
• WHITE, RICHARD GRANT (1822-1885)
• WHITE, ROBERT (1645-1704)
• WHITE, SIR GEORGE STUART (1835– )
• WHITE, SIR THOMAS (1492-1567)
• WHITE, SIR WILLIAM ARTHUR (1824--1891)
• WHITE, SIR WILLIAM HENRY (1845– )
• WHITE, THOMAS (1628-1698)
• WHITE, THOMAS (c. 1550-1624)

white, but it is often tinted, especially in the alabaster variety, See also:

• GREY, CHARLES GREY, 2ND EARL (1764-1845)
• GREY, HENRY GREY, 3RD EARL (1802-1894)
• GREY, LADY JANE (1537-1554)
• GREY, SIR EDWARD
• GREY, SIR GEORGE (1812–1898)

grey, yellow or See also:

• PINK

pink . Gypsum crystallizes with two molecules of water, equal to about 21 % by See also:

• WEIGHT

weight, and consequently has the See also:

• FORMULA
• FORMULA (Lat. diminutive of forma, shape, pattern, &c., especially used of rules of judicial procedure)

formula CaSO4•2H20 . By exposure to strong See also:

• HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat all the water may be expelled, and the substance then has the See also:

• COMPOSITION
• COMPOSITION (Lat. compositio, from componere, to put together)

composition of See also:

• ANHYDRITE

anhydrite (q.v.) .

When the calcination, however, is conducted at such a temperature that only about 75% of the water is lost, it yields a white pulverulent substance, known as " plaster of See also:

• PARIS
• PARIS (also called ALEXANDROS)
• PARIS, ALEXIS PAULIN (1800-x881)
• PARIS, BRUNO PAULIN GASTON (1839-1903)
• PARIS, FRANCOIS DE (169o-1727)
• PARIS, LOUIS PHILIPPE ALBERT
• PARIS, TREATIES OF (1814-1815)

Paris," which may readily be caused to recombine with water, forming a hard See also:

• CEMENT (from Lat. caementum, rough pieces of stone, a shortened form of caedimentum, from caedere, to cut)

cement . The gypsum quarries of Montmartre, in the See also:

• NORTH
• NORTH, BARONS
• NORTH, MARIANNE (1830—1890)
• NORTH, ROGER (1653-1734)
• NORTH, SIR THOMAS (1535?-16o1?)

north of Paris, were worked in See also:

• TERTIARY

Tertiary strata, See also:

• RICH, BARNABE (c. 1540-1617)
• RICH, CLAUDIUS JAMES (1787-1821)
• RICH, JOHN (1692-1761)
• RICH, PENELOPE, LADY (c. 1562–1607)
• RICH, RICHARD, 1ST BARON RICH (1490?-1567)

rich in fossils . Gypsum is largely quarried in See also:

• ENGLAND
• ENGLAND, THE CHURCH OF

England for See also:

• CONVERSION (Lat. conversio, from convertere, to turn or ,change)

conversion into plaster of Paris, whence it is sometimes known as " plaster See also:

• STONE
• STONE (0. Eng. shin; the word is common to Teutonic languages, cf. Ger. Stein, Du. steen, Dan. and Swed. sten; the root is also seen in Gr. aria, pebble)
• STONE, CHARLES POMEROY (1824-1887)
• STONE, EDWARD JAMES (1831-1897)
• STONE, FRANK (1800-1859)
• STONE, GEORGE (1708—1764)
• STONE, LUCY [BLACKWELL] (1818-1893)
• STONE, MARCUS (184o— )
• STONE, NICHOLAS (1586-1647)

stone," and since much is sent to the See also:

• STAFFORDSHIRE

Staffordshire See also:

• POTTERIES, THE

potteries for making moulds it is also termed " See also:

• POTTER, ALONZO (1800-1865)
• POTTER, HENRY CODMAN (1835–1908)
• POTTER, J
• POTTER, JOHN (c. 1674-1747)
• POTTER, PAUL (1625—1654)
• POTTER, PHILIP CIPRIANI HAMBLEY (1792—1871)

potter's stone." The See also:

• CHIEF (from Fr. chef, head, Lat. caput)

chief workings are in the Keuper marls near See also:

• NEWARK
• NEWARK (NEWARK-UPON-TRENT)
• NEWARK, DAVID LESLIE, LORD (1601-1682)

Newark in See also:

• NOTTINGHAMSHIRE, or NOTTS

Nottinghamshire, Fauld in Staffordshire and Chellaston in See also:

• DERBYSHIRE

Derbyshire . It is also worked in See also:

• PERMIAN

Permian beds in See also:

• CUMBERLAND
• CUMBERLAND, DUKES AND EARLS OF
• CUMBERLAND, RICHARD (1632-1718)
• CUMBERLAND, RICHARD (1732-1811)
• CUMBERLAND, WILLIAM AUGUSTUS

Cumberland and See also:

• WESTMORLAND
• WESTMORLAND, EARLS OF

Westmorland, and in Purbeck strata near See also:

• BATTLE

Battle in See also:

• SUSSEX
• SUSSEX, EARLS OF
• SUSSEX, KINGDOM OF (SO Seaxe, i.e. the South Saxons)
• SUSSEX, THOMAS RADCLYFFE [or RATCLYFFE], 3RD EARL OF (c. 1525-1583)

Sussex . Gypsum frequently occurs in association with See also:

• ROCK
• ROCK (O.Fr. rake, Sp. rota, Ital. rocca; possibly from a Lat. form rupica, from rupes, rock)
• ROCK, DANIEL (1799–187t)

rock-See also:

• SALT (a common Teutonic word, cf. Dutch zout, Ger. Salz, Scand. salt; cognate with Gr. &Xs, Lat. sal)
• SALT, SIR TITUS, BART

salt, having been deposited in shallow basins of salt water . Much of the calcium in See also:

• SEA (in O. Eng. sae, a common Teutonic word; cf. Ger. See, Dutch Zee, &c.; the ultimate source is uncertain)
• SEA, COMMAND OF THE

sea-water exists as sulphate; and on evaporation of a drop of sea-water under the See also:

• MICROSCOPE (Gr. µucp6s, small, asenreiv, to %view)

microscope this sulphate is deposited as acicular crystals of gypsum . In salt-lagoons the deposition of the gypsum is probably effected in most cases by means of micro-organisms . Waters containing sulphuretted See also:

• HYDROGEN [symbol H, atomic weight x-oo8 (0=16)]

hydrogen, on exposure to the air in the presence of See also:

• LIMESTONE

limestone, may yield gypsum by the formation of sulphuric See also:

• ACID (from the Lat. root ac-, sharp; acere, to be sour)

acid and its interaction with the calcium carbonate . In volcanic districts gypsum is produced by the See also:

• ACTION

action of sulphuric acid, resulting from the oxidation of sulphurous vapours, on See also:

• LIME
• LIME (O. Eng. lim, Lat. limes, mud, from linere, to smear)

lime-bearing minerals, like See also:

• LABRADORITE, or LABRADOR SPAR

labradorite and See also:

• AUGITE

augite, in the volcanic rocks: hence gypsum is common around solfataras . Again, by the oxidation of See also:

• IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron-See also:

• PYRITES

pyrites and the action of the resulting sulphuric acid on limestone or on shells, gypsum may be formed; whence its origin in most See also:

• CLAYS, PAUL JEAN (1819-1900)

clays . Gypsum is also formed in some cases by the hydration of anhydrite, the See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change being accompanied by an increase of See also:

• VOLUME

volume to the extent of about 6o% . Conversely gypsum may, under certain conditions, be dehydrated or reduced to anhydrite .

Some of the largest known crystals of selenite have been found in See also:

• SOUTHERN

southern See also:

• UTAH

Utah, where they occur in huge geodes, or crystal-lined cavities, in deposits from the old salt-lakes . See also:

• FINE

Fine crystals, sometimes curiously See also:

• BENT
• BENT (E1. BENI)
• BENT, JAMES THEODORE (1852–1897)

bent, occur in the Permian rocks of See also:

• FRIEDRICHRODA

Friedrichroda, near See also:

• GOTHA

Gotha, where there is a grotto called the Marienglashohle, See also:

• CLOSE
• CLOSE (from Lat. clausum, shut)
• CLOSE, MAXWELL HENRY (1822-1903)

close to Rheinhardsbrunn . Many of the best localities for selenite are in the New Red See also:

• SANDSTONE

Sandstone formation (Trias and Permian), notably the salt-mines of See also:

• HALL
• HALL (generally known as SCHWABISCH-HALL, tc distinguish it from the small town of Hall in Tirol and Bad-Hall, a health resort in Upper Austria)
• HALL (O.E. heall, a common Teutonic word, cf. Ger. Halle)
• HALL, BASIL (1788-1844)
• HALL, CARL CHRISTIAN (1812–1888)
• HALL, CHARLES FRANCIS (1821-1871)
• HALL, CHRISTOPHER NEWMAN (1816—19oz)
• HALL, EDWARD (c. 1498-1547)
• HALL, FITZEDWARD (1825-1901)
• HALL, ISAAC HOLLISTER (1837-1896)
• HALL, JAMES (1793–1868)
• HALL, JAMES (1811–1898)
• HALL, JOSEPH (1574-1656)
• HALL, MARSHALL (1790-1857)
• HALL, ROBERT (1764-1831)
• HALL, SAMUEL CARTER (5800-5889)
• HALL, SIR JAMES (1761-1832)
• HALL, WILLIAM EDWARD (1835-1894)

Hall and Hallein, near See also:

• SALZBURG

Salzburg, and of Bex in See also:

• SWITZERLAND

Switzerland . Excellent crystals, usually of a brownish See also:

• COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour arranged in See also:

• GROUPS
• GROUPS, THEORY

groups, are often found in the brine-See also:

• CHAMBERS (the Fr. chambre, from Lat. camera, a room)
• CHAMBERS, EPHRAIM (d. 1740)
• CHAMBERS, GEORGE (1803-1840)
• CHAMBERS, ROBERT (18oz-1871)
• CHAMBERS, SIR WILLIAM (1726-1796)

chambers and the launders used in salt-See also:

• WORKS

works . Selenite also occurs in fine crystals in the See also:

• SULPHUR

sulphur-bearing marls of See also:

• GIRGENTI (anc. Agrigent'um, q.v.)

Girgenti and other Sicilian localities; whilst in See also:

• BRITAIN (Gr. Hperavuml vi7vot, Bperravia; Lat. Britannia, rarely Britannia)

Britain very bold crystals are yielded by the Kimeridge clay of Shotover See also:

• HILL
• HILL (0. Eng. hyll; cf. Low Ger. hull, Mid. Dutch hul, allied to Lat. celsus, high, collis, hill, &c.)
• HILL, A
• HILL, AARON (1685-175o)
• HILL, AMBROSE POWELL
• HILL, DANIEL HARVEY (1821-1889)
• HILL, DAVID BENNETT (1843–1910)
• HILL, GEORGE BIRKBECK NORMAN (1835-1903)
• HILL, JAMES J
• HILL, JOHN (c. 1716-1775)
• HILL, MATTHEW DAVENPORT (1792-1872)
• HILL, OCTAVIA (1838– )
• HILL, ROWLAND (1744–1833)
• HILL, SIR ROWLAND (1795-1879)

Hill near See also:

• OXFORD
• OXFORD, EARLS OF
• OXFORD, EDWARD DE VERE, 17TH EARL
• OXFORD, JOHN DE VERE, 13TH EARL OF (1443-1513)
• OXFORD, PROVISIONS OF
• OXFORD, ROBERT DE VERE, 9TH EARL OF (1362-1392)
• OXFORD, ROBERT HARLEY, 1ST

Oxford . See also:

• TWISTED

Twisted crystals and rosettes of gypsum found in the See also:

• MAMMOTH
• MAMMOTH (0. Russ. mammot, mod. mamant; the Tatar word mama, earth, from which it is supposed to be derived, is not known to exist)

Mammoth See also:

• CAVE (Lat. cavea, from caves, hollow)
• CAVE, EDWARD (1691–1754)
• CAVE, WILLIAM (1637–1713)

Cave, See also:

• KENTUCKY

Kentucky, have been called " oulopholites " (ovXos, " woolly "; qSwXe6s, " cave ") . In addition to the use of gypsum in cement-making, the mineral finds application as an agricultural See also:

• AGENT (from Lat. agere, to act)

agent in dressing See also:

• LAND

land, and it has also been used in the manufacture of See also:

• PORCELAIN

porcelain and See also:

• GLASS
• GLASS (O.E. glees, cf. Ger. Glas, perhaps derived from an old Teutonic root gla-, a variant of glo-, having the general sense of shining, cf. " glare," " glow ")
• GLASS, STAINED

glass . Formerly it was employed, in the form of thin cleavage-plates, for See also:

• GLAZING

glazing windows, and seems to have been, with See also:

• MICA

mica, called lapis specularis . It is still known in See also:

• GERMANY
• GERMANY (Ger. Deutschland)

Germany as Marienglas and Fraueneis . Delicate cleavage-plates of gypsum are used in microscopic petrography for the determination of certain See also:

• OPTICAL

optical constants in the rock-forming minerals . (F . W .