See also:

• FELSPAR, or FELDSPAR

FELSPAR, or FELDSPAR  , a name applied to a See also:

• GROUP

group of See also:

• MINERAL

mineral silicates of much importance as 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-constituents . The name, taken from the Ger . Feldspath, was originally written with a " d " but in 1794 it was written " See also:

• FELSPAR, or FELDSPAR

felspar " by R . See also:

• KIRWAN, RICHARD (1733-1812)

Kirwan, on the See also:

• ASSUMPTION, FEAST OF

assumption that it denoted a mineral of the " Eels " rather than of the " See also:

• FIELD (a word common to many West German languages, cf. Ger. Feld, Dutch veld, possibly cognate with O.E. f olde, the earth, and ultimately with root of the Gr. irAaror, broad)
• FIELD, CYRUS WEST (1819-1892)
• FIELD, DAVID DUDLEY (18o5-1894)
• FIELD, EUGENE (1850-1895)
• FIELD, FREDERICK (18o1—1885)
• FIELD, HENRY MARTYN (1822-1907)
• FIELD, JOHN (1782—1837)
• FIELD, MARSHALL (183 1906)
• FIELD, NATHAN (1587—1633)
• FIELD, STEPHEN JOHNSON (1816-1899)
• FIELD, WILLIAM VENTRIS FIELD, BARON (1813-1907)

field," and this corrupted See also:

• FORM (Lat. forma)

form is now in See also:

• COMMON

common use in See also:

• ENGLAND
• ENGLAND, THE CHURCH OF

England . By some of the earlier mineralogists it was written " feltspar," from the See also:

• SWEDISH

Swedish form fdltspat . The felspar - group is divided into two subgroups according to the symmetry of the crystals . Although the crystals of all felspars See also:

• PRESENT

present a See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

general resemblance in 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, they are usually regarded as belonging to two systems, some felspars being mono-clinic and others anorthic . Figures of the crystals are given in the articles on the different See also:

• SPECIES

species . Two cleavages are generally well marked . In the See also:

• MONOCLINIC

monoclinic or monosymmetric felspars these, being parallel to the basal pinacoid and clinopinacoid, necessarily make an See also:

• ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

angle of 900, whence the name See also:

• ORTHOCLASE

orthoclase applied to these minerals; whilst in the anorthic or See also:

• ASYMMETRIC

asymmetric felspars the corresponding angle is never exactly 900, and from this obliquity of the See also:

• PRINCIPAL

principal cleavages they are termed See also:

• PLAGIOCLASE

plagioclase (see ORTHOCLASE and PLAGIOCLASE) . There are consequently two See also:

• SERIES (a Latin word from serere, to join)

series of felspars, one termed orthoclastic or orthotomous, and the other plagioclastic or clinotomous . F .

E . Mallard suggested that all felspars are really asymmetric, and that orthoclase presents only a pseudo-monosymmetric habit, due to twinning . Twin-crystals are very common in all the felspars, as explained under their respective headings . The two divisions of the felspar-group founded on See also:

• DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences of crystalline symmetry are subdivided according to chemical See also:

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

composition . All the felspars are silicates containing See also:

• ALUMINIUM (symbol Al; atomic weight 27.0)

aluminium with some other metallic See also:

• BASE

base or bases, generally See also:

• POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)]

potassium, See also:

• SODIUM [symbol Na, from Lat. natrium; atomic weight 23.00 (0=16)]

sodium or See also:

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

calcium, rarely See also:

• BARIUM (symbol Ba, atomic weight 137'37 [0=16])

barium, but never See also:

• MAGNESIUM [symbol Mg, atomic weight 24.32 (0 = 16)]

magnesium or See also:

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

iron . The monoclinic series includes common potash-felspar or orthoclase (KAlSi3O8) and hyalophane, a rare felspar containing barium (K2BaA14Si8O24)• The anorthic series includes at one end the soda-felspar See also:

• ALBITE

albite (NaAlSi3O8) and at the other extremity the See also:

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

lime-felspar See also:

• ANORTHITE

anorthite (CaAl2Si2O8) . It was suggested by G . Tschermak in 1864 that the other plagioclastic felspars are isomorphous mixtures in various proportion of albite (Ab) and anorthite (An) . These intermediate members are the lime-soda felspars known as See also:

• OLIGOCLASE

oligoclase, See also:

• ANDESINE

andesine, See also:

• LABRADORITE, or LABRADOR SPAR

labradorite and See also:

• BYTOWNITE

bytownite . There are also placed in the anorthic class a potash-felspar called See also:

• MICROCLINE

microcline, and a rare soda-potash-felspar known as anorthoclase . The specific gravity of the felspars has been shown by G . Tschermak and V .

See also:

• GOLDSCHMIDT, HERMANN (1802-1866)

Goldschmidt to vary according to their chemical composition, rising steadily from 2.57 in orthoclase to 2.75 in anorthite . All the felspars have a hardness of 6 to 6.5, being therefore rather less hard than See also:

• QUARTZ

quartz . Pure felspar is colourless, but the mineral is usually 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, yellow, red or See also:

• GREEN, A
• GREEN, ALEXANDER HENRY (1832—1896)
• GREEN, DUFF (1791—1875)
• GREEN, JOHN RICHARD (1837—1883)
• GREEN, MATTHEW (1696-1737)
• GREEN, THOMAS HILL (1836-1882)
• GREEN, VALENTINE (1739–1813)
• GREEN, WILLIAM HENRY (.1825–1900)

green . Certain felspars are used as ornamental stones on See also:

• ACCOUNT
• ACCOUNT (through O. Fr. acont, Late Lat. comptum, cornputare, to calculate)

account of their See also:

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

colour (see See also:

• AMAZON

AMAZON.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) . Other felspars are prized for their pearly opalescence (see See also:

• MOONSTONE

MOONSTONE), or for their See also:

• PLAY

play of iridescent See also:

• COLOURS, MILITARY

colours (see LABRADORITE), or for their spangled See also:

• APPEARANCE (from Lat. apparere, to appear)

appearance, like See also:

• AVENTURINE, or AVANTURINE

aventurine (see See also:

• SUN
• SUN (0. Eng. sonne, Ger. sonne. Fr. soleil, Lat. sol, Gr. ijXior, from which comes helio- in various English compounds)

SUN-STONE) . Felspar is much used in the manufacture of See also:

• PORCELAIN

porcelain by See also:

• REASON (Lat. ratio, through French raison)

reason of its fusibility . In England the material employed is mostly orthoclase from Scandinavia, often known as " Swedish spar." The high translucency of " See also:

• IVORY (Fr. ivoire, Lat. ebur)
• IVORY, SIR JAMES (1765-1842)

ivory porcelain " depends on the large proportion of felspar in the See also:

• BODY

body . The mineral is also an important constituent of most ceramic glazes . The melting points of felspars have been investigated by Prof . J . Joly, Prof . C .

A . Doelter y Cisterich and especially by A . L . See also:

• DAY (O. Eng. dreg, Ger. Tag; according to the New English Dictionary, " in no way related to the Lat. dies")
• DAY, JOHN (1574-1640?)
• DAY, THOMAS (1748-1789)

Day and E . T . See also:

• ALLEN, BOG OF
• ALLEN, ETHAN (1739–1789)
• ALLEN, GRANT CHARLES GRANT BLAIRFINDIEI, (1848–1899)
• ALLEN, JAMES LANE (1850– )
• ALLEN, JOHN (1476–1534)
• ALLEN, or ALLEYN, THOMAS (1542-1632)
• ALLEN, WILLIAM (1532-1594)
• ALLEN, WILLIAM FRANCIS (183o-1889)

Allen in the Geophysical Laboratory of the See also:

• CARNEGIE
• CARNEGIE, ANDREW (1837– )

Carnegie See also:

• INSTITUTE (from Lat. instituere, to establish or set up)

Institute at See also:

• WASHINGTON
• WASHINGTON (or WASHINGTON COURT HOUSE)
• WASHINGTON, BOOKER TALIAFERRO (c. 1859– )
• WASHINGTON, BUSHROD (1762-1829)
• WASHINGTON, GEORGE (1732-1799)

Washington . Among the applications of feispar is that of pure orthoclase in the manufacture of artificial See also:

• TEETH (O.E. Eel); plural of tooth, O.E. top)

teeth . Felspar readily suffers chemical alteration, yielding See also:

• KAOLIN

kaolin (q.v.) . The turbidity of orthoclase is usually due to partial kaolinization . Secondary See also:

• MICA

mica is also a common result of alteration, and among other products are pinite, See also:

• EPIDOTE

epidote, saussurite, See also:

• CHLORITE

chlorite, See also:

• WOLLASTONITE

wollastonite and various See also:

• ZEOLITES

zeolites . See ALBITE, AMAZON STONE, ANDESINE, ANORTHITE, BYTOWNITE, LAB RADORITE,MIC ROCLINE, MOONSTONE,OLIGOCLASE,ORTHOCLASE, PLAGIOCLASE, SUN-STONE .