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BARYTES , a widely distributed See also:mineral composed of See also:barium sulphate (BaSO4). Its most striking feature and the one from which it derives its name barytes, barite (from the See also:Greek Oapvs, heavy) or heavy spar, is its See also:weight. Its specific gravity of 4.5 is about twice as See also:great as that of See also:salt and of many other colourless, transparent and glassy minerals not unlike barytes in See also:general See also:appearance. The mineral is usually found in a See also:state of consider-able chemical purity, though small amounts of See also:strontium and See also:calcium sulphates may isomorphously replace the barium sulphate: ammonium sulphate is also sometimes See also:present, whilstclay, See also:silica, bituminous See also:matter, &c., may be enclosed as impurities.
Crystals of barytes are orthorhombic and isomorphous with the strontium and See also:lead sulphates (celestite and anglesite) ; they are usually very perfectly See also:developed and present great variety of See also:form. The simplest are rhomb-shaped tables (fig. 1) bounded by the two faces of the basal pinacoid (c) and the four faces of the See also:prism (m); the See also:angle between the prism-faces (mm) is 78° 23', whilst that between c and m is 9o°. The mineral has a very perfect cleavage parallel to the faces c and m, and the cleavage surfaces are perfectly smooth and See also:bright. The crystals of prismatic See also:habit represented in See also:figs. 2 and 3 are bounded by the domes d and f and the basal pinacoid c; fig. 4 is a See also:plan of a still
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more complex crystal. Twinning is represented only by twin-lamellae, which are parallel to the planes m and f and are of secondary origin, having been produced by pressure.
Crystals of barytes may be transparent and colourless, or 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 and opaque, or of a yellow, 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, bluish or greenish See also:colour. Well developed crystals are extremely See also:common, but the mineral occurs also in a granular, earthy, or stalactitic See also:condition. It is known as cawk in the See also:Derbyshire lead mines. The " crested " or " See also:cock's See also:comb " barytes occurs as rounded aggregations of thin lamellar crystals.
Barytes is of common occurrence in metalliferous See also:veins, especially those which yield ores of lead and See also:silver; some of the largest and most perfect crystals of colourless barytes were obtained from the lead mines near Duf ton in See also:Westmorland. It is found also in beds of See also:iron ore, and the See also:haematite mines of the Cleator See also:Moor See also:district in See also:west See also:Cumberland have yielded many extremely See also:fine crystals, specimens of which may be seen in all mineral collections. In the neighbourhood of See also:Nottingham, and other places in the Midlands, barytes forms a cementing material in the Triassic sandstones; See also:amber-coloured crystals of the same mineral are found in the See also:fuller's See also:earth at Nutfield in See also:Surrey; and the septarian nodules in See also:London See also:Clay contain crystals of barytes as well as of See also:calcite. Crystals are found as a rarity in the amygdaloidal cavities of igneous rocks.
Artificially prepared crystals of barytes may be obtained by allowing a See also:solution of a soluble barium salt to diffuse slowly into a solution of a soluble sulphate. Barium chloride is present in some natural See also:waters, and when this is the See also:case the interaction of sulphates results in a deposition of barytes, as has occurred in the pipes and See also:water-boxes of the See also:Newcastle-on-See also:Tyne See also:coal mines.
Commercially, barytes is used in the preparation of barium compounds, as a See also:body for certain kinds of See also:paper and See also:cloth, and as a white pigment (" permanent white "). The finely powdered and washed mineral is too crystalline and consequently of insufficient opacity to be used alone as a paint, and is therefore mixed with " white lead," of which material it is also used as an adulterant.
(L. J.
End of Article: BARYTES
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