See also:

• PEGMATITE (from Gr. 1r3 y ea, a bond)

PEGMATITE (from Gr. 1r3 y See also:

• EA(nar...), (p.s„,.,.)
• EA(psr...), (p, „...)• (pqr...)

ea, a See also:

• BOND
• BOND, SIR EDWARD AUGUSTUS (1815-1898)

bond)  , the name given by Hairy to those masses of graphic See also:

• GRANITE (adapted from the Ital. granite, grained; Lat. granum, grain)

granite which frequently occur in See also:

• VEINS

veins . They consist of See also:

• QUARTZ

quartz and See also:

• ALKALI

alkali feldspars in crystalline intergrowth (see See also:

• PETROLOGY

PETROLOGY, See also:

• PLATE

Plate II. fig . 6) . The See also:

• TERM

term was subsequently used by See also:

• NAUMANN, GEORG AMADEUS CARL FRIEDRICH (1797-1873)

Naumann to signify also the coarsely crystalline veins 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 quartz, feldspar and See also:

• MUSCOVITE

muscovite, which often in See also:

• GREAT

great See also:

• NUMBERS, BOOK OF
• NUMBERS, PARTITION OF

numbers ramify through outcrops of granite and the surrounding locks . This application of the name has now from which they are derived, e.g. granite-pegmatites contain principally quartz and feldspar while See also:

• GABBRO

gabbro-pegmatites consist of See also:

• DIALLAGE

diallage and See also:

• PLAGIOCLASE

plagioclase . Rare minerals, however, often occur in .these veins in exceptional amount and as very perfect crystals . The minerals of the pegmatites are always those which were last to See also:

• SEPARATE

separate out from the See also:

• PARENT, SIMON NAPOLEON (1855– )

parent 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 . As the basic minerals are the first formed the pegmatites contain a larger proportion of the See also:

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

acid or more siliceous components which were of later origin . In granite-pegmatites there is little See also:

• HORNBLENDE

hornblende, See also:

• BIOTITE

biotite or See also:

• SPHENE

sphene, but 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 See also:

• MICA

mica, feldspar and quartz make up the greater See also:

• PART

part of the veins . In gabbro-pegmatites See also:

• OLIVINE

olivine seldom occurs, but diallage and plagioclase occur in abundance . In this respect the pegmatites and aplites agree; both are of more acid types than the See also:

• AVERAGE

average rock from which they came, but the pegmatites are coarsely crystalline while the aplites are See also:

• FINE

fine-grained . Segregations of the See also:

• EARLY
• EARLY, JUBAL ANDERSON (1816-1894)

early minerals of a rock are frequent as nodules, lumps and streaks scattered through its See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

mass, and often dikes of basic See also:

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

character (See also:

• LAMPROPHYRES (from Gr. Xaurp6s, bright, and the terminal part of the word porphyry, meaning rocks containing bright porphyritic crystals)

lamprophyres, &c.) are injected into the surrounding See also:

• COUNTRY (from the Mid. Eng. contre or contrie, and O. Fr. cuntree; Late Lat. contrata, showing the derivation from contra, opposite, over against, thus the tract of land which fronts the sight, cf. Ger. Gegend, neighbourhood)

country .

These have been grouped together as intrusions of melanocrate facies (,uAas, See also:

• BLACK
• BLACK, ADAM (1784-1874)
• BLACK, JEREMIAH SULLIVAN (1810–1883)
• BLACK, WILLIAM (1841-1898)

black, KpaTOS, strength, predominance) because in them the dark basic minerals preponderate . The aplites and pegmatites, on the other See also:

• HAND
• HAND (a word common to Teutonic languages; cf. Ger. Hand, Goth. handus)
• HAND, FERDINAND GOTTHELF (1786-185r)

hand, are leucocrate (Aevsbs, white), since they are of acid character and contain relatively large amounts of the white minerals quartz and feldspar . pegmatites are associated with plutonic or intrusive rocks and were evidently formed by slow See also:

• CRYSTALLIZATION

crystallization at considerable depths below the See also:

• SURFACE

surface: nothing similar to them is known in lavas . They are very characteristic of granites, especially those which contain muscovite and much alkali feldspar; in gabbros, diorites and syenites pregmatite dikes are comparatively rare . The coarsely crystalline structure may be ascribed to slow crystallization; and is partly the result of the rocks, in which the veins See also:

• LIE, JONAS LAURITZ EDEMIL (1833—1908)
• LIE, MARIUS SOPHUS (1842–1899)

lie, having been at a high temperature when the minerals of the pegmatites separated out . In accordance with this we find that See also:

• PEGMATITE (from Gr. 1r3 y ea, a bond)

pegmatite veins are nearly always restricted to the See also:

• AREA

area occupied by the parent rock (e.g. the granite), or to its immediate vicinity, and within the See also:

• ZONE (Gr. 'WV77, a girdle, from 'wvvLvay to gird)

zone which has been greatly heated by the plutonic intrusion, viz. the contact aureole . Another very important See also:

• FACTOR (from Lat. facere, to make or do)

factor in producing the coarse crystallization of the pegmatite veins is the presence of abundant See also:

• WATER

water vapour and other gases which served as mineralizing agents and facilitated the See also:

• BUILDING

building together of the rock molecules in large crystalline individuals . See also:

• PROOF (in M. Eng. preove, proeve, preve, &°c., from O. Fr . prueve, proeve, &c., mod. preuve, Late. Lat. proba, probate, to prove, to test the goodness of anything, probus, good)

Proof that these vapours were important agents in the formation of pegmatites is afforded by many of the minerals contained in the veins . See also:

• BORON (symbol B, atomic weight I I)

Boron, See also:

• FLUORINE (symbol F, atomic weight 19)

fluorine, See also:

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

hydrogen, See also:

• CHLORINE (symbol Cl, atomic weight 35`46 (0=16)

chlorine and other volatile substances are essential components of some of these minerals . Thus See also:

• TOURMALINE

tourmaline, which contains boron and fluorine, may be See also:

• COMMON

common in the pegmatites but rare in the granite itself . Fluorine or chlorine are See also:

• PRESENT

present in See also:

• APATITE

apatite, another frequent ingredient of granite pegmatites . Muscovite and gilbertite both contain hydrogen and fluorine; See also:

• TOPAZ

topaz is rich in fluorine also and all of these are abundant in some pegmatites .

The stimulating effect which volatile substances exert on crystallizing molten masses is well known to experimental geologists who, by mixing tungstates and fluorides with fused powders, have been able to produce artificial minerals which they could not otherwise obtain . Most pegmatites are truly igneous rocks so far as their See also:

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

composition goes, but in their structure they show relations to the aqueous See also:

• MINERAL

mineral veins . Many of them for example have a comby structure, that is to say, their minerals are columnar and stand perpendicular to the walls of the fissure occupied by the vein . Sometimes they have a banding owing to successive deposits having been laid down of different character; mica may be See also:

• EXTERNAL

external, then feldspar, and in the centre a See also:

• LEADER, BENJAMIN WILLIAMS (1831– )

leader or See also:

• STRING

string of pure quartz . In pegmatite veins also there are very frequently cavities or vugs, which are lined by crystals with very perfect faces . These See also:

• BEAR
• BEAR, BLACK
• BEAR, BROWN
• BEAR, GRIZZLY
• BEAR, ISABELLINE
• BEAR, WHITE

bear much resemblance to the miarolitic or drusy cavities common in granite, and like them were probably filled with the residual liquid which was See also:

• LEFT

left over after the mineral substances were deposited in crystals . Pegmatites are very irregular not only in See also:

• DISTRIBUTION (Lat. distribuere, to deal out)

distribution, width and persistence, but also in composition . The relative abundance of the constituent minerals may differ rapidly and much from point to point . Sometimes they are rich in mica, in enormous crystals for which the rock is See also:

• MINED

mined or quarried (See also:

• INDIA
• INDIA, FRENCH

India) . Other pegmatites are nearly pure feldspar, while others are locally (especially near their terminations) very full of quartz . They may in fact pass into quartz veins (alaskites) some of which are auriferous (N . See also:

• AMERICA

America) .

Quartz veins of another type are very largely See also:

• DEVELOPED

developed, especially in regions of See also:

• SLATE (properly CLAY SLATE; in M. Eng. slat or sclat, from O. Fr. esclat, a small piece of wood used as a tile; esclater, to break into pieces, whence modern Fr. eclat, the root being seen also in Ger. schleissen, to split)

slate and See also:

• PHYLLITE (Gr. 40)XAov, a leaf, probably because they yield leaf-like plates, owing to their fissility)

phyllite; they are produced by segregation of dissolved See also:

• SILICA

silica from the country rock and its concentration into cracks produced by stretching of the rock masses during folding . In these segregation veins, especially when the beds are of feldspathic nature, crystals of See also:

• ALBITE

albite and See also:

• ORTHOCLASE

orthoclase may appear, in large or small quantity . In this way a second type of pegmatite (segregation pegmatite) is formed which is very difficult to distinguish from true igneous veins . These two have, however, much in common as regards the conditions under which they were formed . Great pressures, presence of water, and a high though not necessarily very high temperature were the See also:

• PRINCIPAL

principal agencies at See also:

• WORK

work . Granite pegmatites are laid down after their parent mass had solidified and while it was cooling down: sometimes they contain such minerals as See also:

• GARNET
• GARNET, or GARNETT, HENRY (1555—1606)

garnet, not found in the See also:

• MAIN (from the Aryan root which appears in " may " and " might," and Lat. magnus, great)
• MAIN (Lat. Moenus)

main mass, and showing that the temperature of crystallization was comparatively See also:

• LOW, SETH (1850- )
• LOW, WILL HICOK (1853- )

low . Another See also:

• SPECIAL

special feature of these veins is the presence of minerals containing See also:

• PRECIOUS (O. Fr. precios, mod. precieux, Lat. pretiosus, of high value or price, pretium)

precious metals or rare earths . See also:

• GOLD
• GOLD [symbol Au, atomic weight 195.7(H = 1),197.2(0 =16)]

Gold occurs in not a few cases; See also:

• TIN (Lat.- stannum, whence the chemical symbol " Sn "; atomic weight =117.6, 0=16)

tin in others, while sulphides such as See also:

• COPPER (symbol Cu, atomic weight 63.1, H=1, or 63.6, O = 16)

copper See also:

• PYRITES

pyrites are found also . See also:

• BERYL

Beryl is the commonest of the minerals of the second See also:

• GROUP

group: See also:

• SPODUMENE

spodumene is another example, and there is much See also:

• REASON (Lat. ratio, through French raison)

reason to hold that See also:

• DIAMOND

diamond is a native of some of the pegmatites of See also:

• BRAZIL
• BRAZIL, or BRASIL

Brazil and India, though this is not yet incogtestably proved . The syenitcpegmatites of See also:

• SOUTH
• SOUTH, ROBERT (1634–1716)

south See also:

• NORWAY
• NORWAY (Norge)

Norway are remarkable both for their coarse crystallization and for the great number of rare minerals they have yielded . Among these may be mentioned laavenite, rinkite, rosenbuschite, mosandrite, pyrochlore, perofskite and lamprophyllite . (J .

S .