See also:ECLOGITE (from Gr. EKXoyi, a selection)
, in See also:petrology, a typical member of a small See also:group of metamorphic rocks of See also:special See also:interest on See also:account of the variety of minerals they contain and their microscopic structures and See also:geological relationships
.
Typically they consist of See also:pale See also:green or nearly colourless See also:augite (omphacite), green See also:hornblende and See also:pink See also:garnet
.
See also:Quartz also is usually See also:present in these rocks,. but See also:felspar is rare
.
The augite is mostly a variety of See also:diopside and is only occasionally idiomorphic
.
The garnet sometimes forms See also:good dodecahedra, but may occur as rounded grains, and encloses quartz, See also:rutile, kyanite, and other minerals very frequently
.
The hornblende is usually pale green and feebly dichroic, but, in some eclogites which are allied to garnet-amphibolites, it is of 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 See also:colour
.
Among the commoner See also:accessory minerals are kyanite (of See also:blue or greyish-blue tints), rutile, See also:biotite, See also:epidote and See also:zoisite, See also:sphene, See also:iron oxides, and
B.C
.
2000; obi
.
=23° 55.5' A.D
.
1700; obi
.
=23°
1500 „ =23 52.3 1750 =23
1000 „ =23 48.9 1800 „ =23,
500 „ =23 .45.4 185o „ =23
0 „ =23 41.7 1900 „ =23
A.D
.
500 „ =23 38.0 1950 „ =23
1000 „ =23 34.1 2000 „ =23
1500 „ =23 30.3 2050 „ =23
2000 „ =23 26.4 2100 „ =23
2500 =23 22.5
See also:pyrites
.
The rutile is invariably in small brown prisms; the kyanite forms bladed crystals, with perfect cleavage; felspar, if present, belongs to basic varieties See also:rich in See also:lime
.
Other minerals which have been found in eclogites are See also:bronzite, See also:olivine and glaucophane
.
The last mentioned is a See also:bright blue variety of hornblende with striking pleochroism
.
The eclogites in their chemical See also:composition show See also:close See also:affinities to gabbros; they often exhibit relationships in 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 which 'show that they were primarily intrusive rocks of igneous origin, and occasionally See also:con-tact alteration can be traced in the adjacent See also:schists
.
Examples are known in See also:Saxony, See also:Bavaria, See also:Carinthia, See also:Austria, See also:Norway
.
A few eclogites also occur in the See also:north-See also:west See also:highlands of See also:Scotland
.
Glaucophane-eclogites have been met with in See also:Italy and the Pennine See also:Alps
.
Specimens of See also:rock allied to See also:eclogite have been found in the diamantiferous See also:peridotite breccias of See also:South See also:Africa (the so-called " blue ground "), and this has given rise to the theory that these are the See also:parent masses from which the See also:Kimberley diamonds have come
.
(J
.
S
.
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