See also:

• GREYWACKE, or GRAUWACKE (a German word signifying a grey earthy rock)

GREYWACKE, or GRAUWACKE (a See also:

• GERMAN
• GERMAN, DUTCH AND SCANDINAVIAN

German word signifying a 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 earthy 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 designation, formerly more generally used by See also:

• ENGLISH

English geologists than at the See also:

• PRESENT

present 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, for impure, highly composite, gritty rocks belonging to the Palaeozoic systems . They correspond to the sandstones, grits and See also:

• FINE

fine conglomerates of the later periods . Greywackes are mostly 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, 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, yellow or See also:

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

black, dull-coloured, sandy rocks which may occur in thick or thin beds along with slates, limestones, &c., and are abundant in See also:

• WALES (Cymru, Gwalia, Cambria)

Wales, the See also:

• SOUTH
• SOUTH, ROBERT (1634–1716)

south of See also:

• SCOTLAND
• SCOTLAND, CHURCH OF
• SCOTLAND, EPISCOPAL CHURCH OF

Scotland and the See also:

• LAKE
• LAKE, GERARD LAKE, 1ST VISCOUNT (1744-1808)

Lake See also:

• DISTRICT

district of See also:

• ENGLAND
• ENGLAND, THE CHURCH OF

England . They contain a very See also:

• GREAT

great variety of minerals, of which the See also:

• PRINCIPAL

principal are See also:

• QUARTZ

quartz, See also:

• ORTHOCLASE

orthoclase and See also:

• PLAGIOCLASE

plagioclase, See also:

• CALCITE

calcite, See also:

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

iron oxides and graphitic carbonaceous matters, together with (in the coarser kinds) fragments of such rocks as See also:

• FELSITE

felsite, chert, 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:

• GNEISS

gneiss, various See also:

• SCHISTS (Gr. vxq'ecv, to split)

schists, See also:

• QUARTZITE

quartzite . Among other minerals found in them are See also:

• BIOTITE

biotite and See also:

• CHLORITE

chlorite, See also:

• TOURMALINE

tourmaline, See also:

• EPIDOTE

epidote, See also:

• APATITE

apatite, See also:

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

garnet, See also:

• HORNBLENDE

hornblende and See also:

• AUGITE

augite, See also:

• SPHENE

sphene, See also:

• PYRITES

pyrites . The cementing material may be siliceous or argillaceous, and is sometimes calcareous . As a See also:

• RULE

rule greywackes are not fossiliferous, but organic remains may be See also:

• COMMON

common in the finer beds associated with them . Their component particles are usually not much rounded by See also:

• ATTRITION (Lat. attritio, formed from atterere, to rub away)

attrition, and the rocks have often been considerably indurated by pressure and See also:

• MINERAL

mineral changes, such as the introduction of interstitial See also:

• SILICA

silica . In some districts the greywackes are cleaved, but they show phenomena of this See also:

• KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind much less perfectly than the slates . Although the See also:

• GROUP

group is so diverse that it is difficult to characterize mineralogically, it has a well-established See also:

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

place in petrographical classifications, because these See also:

• PECULIAR

peculiar composite arenaceous deposits are very frequent among See also:

• SILURIAN

Silurian and See also:

• CAMBRIAN

Cambrian rocks, and rarely occur in Secondary or See also:

• TERTIARY

Tertiary systems . Their essential features are their gritty See also:

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

character and their complex See also:

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

composition . By increasing See also:

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

metamorphism greywackes frequently pass into See also:

• MICA

mica-schists, chloritic schists and sedimentary gneisses .

(J . S .