See also:

• HORNFELS (a German word meaning hornstone)

HORNFELS (a See also:

• GERMAN
• GERMAN, DUTCH AND SCANDINAVIAN

German word meaning hornstone)  , the See also:

• GROUP

group designation for a See also:

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

series of rocks which have been baked and indurated by the 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 of intrusive granitic masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable . Most hornfelses are See also:

• FINE

fine-grained, and while the See also:

• ORIGINAL

original rocks (such as See also:

• SANDSTONE

sandstone, shale and 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, See also:

• LIMESTONE

limestone and See also:

• DIABASE

diabase) may have been more or less fissile owing to the presence of bedding or cleavage planes, this structure is effaced or rendered inoperative in the See also:

• HORNFELS (a German word meaning hornstone)

hornfels . Though they may show banding, due to bedding, &c., they break across this as readily as along it; in fact they tend to See also:

• SEPARATE

separate into cubical fragments rather than into thin plates . The commonest hornfelses (the " See also:

• BIOTITE

biotite hornfelses ") are dark-See also:

• BROWN
• BROWN, CHARLES BROCKDEN (1771-181o)
• BROWN, FORD MADOX (1821-1893)
• BROWN, FRANCIS (1849- )
• BROWN, GEORGE (1818-188o)
• BROWN, HENRY KIRKE (1814-1886)
• BROWN, JACOB (1775–1828)
• BROWN, JOHN (1715–1766)
• BROWN, JOHN (1722-1787)
• BROWN, JOHN (1735–1788)
• BROWN, JOHN (1784–1858)
• BROWN, JOHN (1800-1859)
• BROWN, JOHN (1810—1882)
• BROWN, JOHN GEORGE (1831— )
• BROWN, ROBERT (1773-1858)
• BROWN, SAMUEL MORISON (1817—1856)
• BROWN, SIR GEORGE (1790-1865)
• BROWN, SIR JOHN (1816-1896)
• BROWN, SIR WILLIAM, BART
• BROWN, THOMAS (1663-1704)
• BROWN, THOMAS (1778-1820)
• BROWN, THOMAS EDWARD (1830-1897)
• BROWN, WILLIAM LAURENCE (1755–1830)

brown to See also:

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

black with a somewhat velvety lustre owing to the abundance of small crystals of shining black See also:

• MICA

mica . The " See also:

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

lime hornfelses " are often 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, 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:

• 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, brown and other See also:

• COLOURS, MILITARY

colours . Green and dark-green are the prevalent tints of the hornfelses produced by the alteration of igneous rocks . Although for the most See also:

• PART

part the constituent grains are too small to be determined by the unaided See also:

• EYE
• EYE (O. Eng. edge, Ger. Auge; derived from an Indo-European root also seen in Lat. oc-ulus, the organ of vision (q.v.)

eye, there are often larger crystals of See also:

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

garnet or See also:

• ANDALUSITE

andalusite scattered through the fine See also:

• MATRIX

matrix, and these may become very prominent on the weathered faces of the 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 . The structure of the hornfelses is very characteristic . Very rarely do any of the minerals show crystalline See also:

• FORM (Lat. forma)

form, but the small grains See also:

• FIT

fit closely together like the fragments of 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; they are usually of nearly equal dimensions and from the resemblance to rough See also:

• PAVEMENT (Lat. pavimentu;n, a floor beaten or rammed hard, from pavire, to beat)

pavement See also:

• WORK

work this has been called' See also:

• PILASTER (Fr. pilastre, med. Lat. pilastrum, from pila, a pillar)

pilaster structure or pavement structure . Each See also:

• MINERAL

mineral may also enclose particles of the others; in the See also:

• QUARTZ

quartz, for example, small crystals of See also:

• GRAPHITE

graphite, biotite, See also:

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

iron oxides, See also:

• SILLIMANITE

sillimanite or See also:

• FELSPAR, or FELDSPAR

felspar may appear in See also:

• GREAT

great See also:

• NUMBERS, BOOK OF
• NUMBERS, PARTITION OF

numbers . Often the whole of the grains are rendered semi-opaque in this way . The minutest crystals may show traces of crystalline outlines; undoubtedly they are of new formation and have originated in situ .

This leads us to believe that the whole rock has been recrystallized at a high temperature and in the solid See also:

• STATE
• STATE, GREAT OFFICERS OF

state, so that there was little freedom for the mineral molecules to build up well-individualized crystals . The regeneration of the rock has been sufficient to efface most of the original structures and to replace the former minerals more or less completely by new ones . But See also:

• CRYSTALLIZATION

crystallization has been hampered by the solid See also:

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

condition of the See also:

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

mass and the new minerals are formless and have been unable to reject impurities, but have grown around them . Slates, shales and See also:

• CLAYS, PAUL JEAN (1819-1900)

clays yield biotite hornfelses in which the most conspicuous mineral is black mica, in small scales which under the See also:

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

microscope are transparent and have a dark reddish-brown See also:

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

colour and strong dichroism . There is also quartz, and often a considerable amount of felspar, while graphite, See also:

• TOURMALINE

tourmaline and iron oxides frequently occur in lesser quantity .