See also:

• MYLONITE (Gr. iwXwv, a mill)

MYLONITE (Gr. iwXwv, a See also:

• MILL
• MILL (O. Eng. mylen, later myln, or miln, adapted from the late Lat. molina, cf. Fr. moulin, from Lat. mola, a mill, molere, to grind; from the same root, mol, is derived " meal;" the word appears in other Teutonic languages, cf. Du. molen, Ger. muhle)
• MILL, JAMES (1773-1836)
• MILL, JOHN (c. 1645–1707)
• MILL, JOHN STUART (1806-1873)

mill)  , in See also:

• PETROLOGY

petrology, a 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 which has been crushed and ground down by See also:

• EARTH
• EARTH (a word common to Teutonic languages, cf. Ger. Erde, Dutch aarde, Swed. and Dan. jord; outside Teutonic it appears only in the Gr. 'pq'e, on the ground; it has been connected by some etymologists with the Aryan root ar-, to plough, which is seen in
• EARTH, FIGURE OF
• EARTH, FIGURE OF THE

earth See also:

• MOVEMENT

movement and at the same See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time rendered compact by pressure . Mylonites are See also:

• FINE

fine-grained, sometimes even flinty, in See also:

• APPEARANCE (from Lat. apparere, to appear)

appearance, and often banded in parallel See also:

• FASHION (adapted from Fr. facon, agon, Lat. factio, making, facere, to do or make)

fashion with stripes of varying See also:

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

composition . The See also:

• GREAT

great See also:

• MAJORITY (Fr. majorite; Med. Lat. majoritas; Lat. major, greater)

majority are quartzose rocks, such as See also:

• QUARTZITE

quartzite and See also:

• QUARTZ

quartz-schist; but in almost any type of rock mylonitic structure may be See also:

• DEVELOPED

developed . Gneisses of various kinds, See also:

• HORNBLENDE

hornblende-See also:

• SCHISTS (Gr. vxq'ecv, to split)

schists, See also:

• CHLORITE

chlorite-schists and limestones are not infrequently found in belts of mylonitic rock . The See also:

• PROCESS

process of crushing by which mylonites are formed is known also as " granulitization " and " cataclasis," and mylonites are often described as granulites, though the two terms are not strictly See also:

• EQUIVALENT

equivalent in all their applications . Mylonites occur in regions where there has been considerable See also:

• METAMORPHISM (Gr. ise-rci, change of, and liop¢i, shape)

metamorphism . Thrust planes and great reversed faults are often bounded by rocks which have all been crushed to fine slabby mylonites, that split readily along planes parallel to the direction in which movement has taken See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place . These " crush-belts " may be only a few feet or several See also:

• HUNDRED

hundred yards broad . The movements have probably taken place slowly without great rise of temperature, and hence the rocks have not recrystallized to any extent . Crushing and movement on so extensive a See also:

• SCALE
• SCALE (1) A

scale are to be expected principally in regions consisting of rocks greatly folded and compressed . Hence mylonites are commonest in Archean regions, but may be found also in Carboniferous and later rocks where the necessary conditions have prevailed . Within a See also:

• SHORT, FRANCIS JOB (1857– )

short space it is often possible to trace rocks from a normal to a highly mylonized See also:

• CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

condition, and to follow by means of the See also:

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

microscope all the stages of the process .

A See also:

• SANDSTONE

sandstone, grit, or fine quartzose See also:

• CONGLOMERATE (from the Lat. conglomerare, to form into a ball, glomus, glomeris; so also the general term " conglomeration " for a miscellaneous collection of things, gathered together in a mass)

conglomerate, for example, when it approaches a mylonitic See also:

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

zone begins to lose its clastic or pebbly structure . The rounded grains of quartz become cracked, especially near their edges, and are then surrounded by narrow See also:

• BORDERS, THE

borders, consisting of detached granules: this is due to the pebbles being pressed together and forced to pass one another as the rock yields to the pressures which overcome its rigidity . Then each quartz See also:

• GRAIN (derived through the French from Lat. granum, seed, from an Aryan root meaning " to wear down," which also appears in the common Teutonic word " corn ")

grain breaks up into a See also:

• MOSAIC (corresponding to Lat. opus musivum, from Gr. µovoeiov, an artificial grotto often decorated with mosaics; the word is only found in the sense of mosaic in late Greek, which generally uses k oXI yrlµa)

mosaic of little angular fragments; the rounded pebbles are flattened out and become lenticular or cake-shaped . Finally only a small See also:

• OVAL (Lat. ovum, egg)

oval patch of fine interlocking quartz grains is See also:

• LEFT

left to indicate the position of the pebble, and if the See also:

• MATRIX

matrix is quartzose this gradually blends with it and a See also:

• UNIFORM

uniform fine-grained quartzose rock results . If See also:

• FELSPAR, or FELDSPAR

felspar is See also:

• PRESENT

present it may become crushed like quartz, but often tends to recrystallize as quartz and See also:

• MUSCOVITE

muscovite, the See also:

• MINUTE
• MINUTE (Lat. minutes, small; minuere, to make less)

minute scales of 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 being parallel to the foliation or banding of the rock, See also:

• WAD

wad a finely granulitic or mylonitic quartz-schist is the product . In hornblendic rocks, such as See also:

• EPIDIORITE

epidiorite, See also:

• AMPHIBOLITE

amphibolite and hornblende-schist, the See also:

• MINERAL

mineral composition may remain unchanged, but very often chlorite, See also:

• CARBONATES

carbonates and See also:

• BIOTITE

biotite develop, See also:

• EPIDOTE

epidote and See also:

• SPHENE

sphene being also frequent . Biotite- and muscovite-gneisses yield very perfect mylonites, in which the micas have parallel See also:

• ORIENTATION

orientation, giving the rock a See also:

• FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat handing and marked schistosity (see PETROLOGY, Pl. iv., fig . 6) . When these myloniticgneisses contain See also:

• PINK

pink See also:

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

garnet (often with kyanite or See also:

• SILLIMANITE

sillimanite) they pass into normal granulites; limestones, if fossiliferous, become changed into finely crystalline masses, often fissile, sometimes with lenticular or augen structure . An interesting variety of See also:

• MYLONITE (Gr. iwXwv, a mill)

mylonite, developed in See also:

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

granite-See also:

• PORPHYRY (IlopcPisptos) (A.D. 233-c. 304)

porphyry and See also:

• GNEISS

gneiss, is fine, dark and almost vitreous in appearance, consisting mainly of very minute grains of quartz and felspar and resembling See also:

• FLINT
• FLINT, AUSTIN (1812-1886)
• FLINT, or FLTNTSHTRE (sir Gallestr)
• FLINT, ROBERT (1838- )
• FLINT, TIMOTHY (1780-1840)

flint in appearance . These See also:

• FORM (Lat. forma)

form threads and vein-like streaks ramifying through the normal rocks . Examples are furnished by the flinty-crushes of See also:

• WEST
• WEST, BENJAMIN (1738-1820)
• WEST, NICHOLAS (1461-1533)

west See also:

• SCOT, MICHAEL (? 1175-1232)

Scot, See also:

• LAND

land and the " See also:

• TRAP (0. Eng. treppe or traepee, properly a step, as that or which an animal places its foot and is caught, cf. Ger. Treppe flight of stairs)

trap-shotten " gneisses of See also:

• SOUTH
• SOUTH, ROBERT (1634–1716)

south See also:

• INDIA
• INDIA, FRENCH

India .

(J . S .