BERYL  , a

mineral containing beryllium and aluminium in the form of a silicate; its formula is Bea All Si6 018 . The species includes the emerald (q.v.), the aquamarine (q.v.) and other trans-parent varieties known as " precious beryl," with certain coarse varieties unfit for use as gem-stones . The name comes from the Gr . 3r1puXXos, a word of uncertain etymology applied to the beryl and probably several other gems . It is notable that the relation of the emerald to the beryl, though proved only by chemical analysis, was conjectured at least as far back as the time of Pliny . Beryl crystallizes in the hexagonal system, usually taking the form of long six-sided prisms, striated vertically and terminated817 with the basal plane, sometimes associated with various pyramidal faces (see fig.) . It cleaves rather imperfectly parallel to the base . The colour of beryl may he blue, green, yellow, brown or rarely pink; while in some cases the mineral is colourless . The specific gravity is about 2.7, and the hardness 7.5 to 8, so that for a gem-stone beryl is comparatively soft . Whilst the gem-varieties are transparent, the coarse beryl may be opaque . The transparent crystals are pleochroic—a character well marked in emerald . Beryl was much prized as a gem-stone by the ancients, and Greek intaglios o very fine workmanship are extant .

The

Roman jewellers, taking advantage of the columnar form of the natural crystal, worked it into long cylinders for ear-pendants . It was a favourite stone with the artists of the Renaissance, but in modern times has lost popularity, except in the form of emerald, which remains one of the most valued gem-stones . It is notable that English lapidaries of the 18th century often included the sard under the term beryl—a practice which has led to some confusion in the nomenclature of engraved gems . Beryl occurs as an accessory constituent of many granitic rocks, especially in veins of pegmatite, whilst it is found also in gneiss and in mica: schist . Rolled pebbles of beryl occur, with topaz, in Brazil, especially in the province of Minas Geraes . Crystals are found in drusy cavities in granite in the Urals, not-ably near Mursinka; in the Altai Mountains, which have yielded very long prismatic crystals; and in the mining district of Nerchinsk in Siberia, principally in the Adun-Chalon range, where beryl occurs in veins of topaz-rock piercing granite . Among European localities may be mentioned Elba, good crystals being occasionally found in the tourmaline-granite of San Piero . In Ireland excellent crystals of beryl occur in druses of the granite of the Mourne Mountains in Co . Down, and others less fine are found in the highlands of Donegal, whilst the mineral is also known from the Leinster granite . It occurs likewise in the granite of the Grampians in Scotland, and is not unknown in Cornwall, specimens having been found, with topaz, apatite, &c., in joints of the granite of St Michael's Mount . Many localities in the United States yield beryl, sometimes sufficiently fine to be cut as a gem . It is found, for example, at Hiddenite and elsewhere in Alexander county, N.C.; at Haddam and Monroe, Conn.; at Stoneham and at Albany, in Oxford county, Maine; at Royalston, Mass.; and at Mt .

Antero,

Colorado, where it occurs with phenacite . Beryl of beautiful pink colour occurs in San Diego county, California . Coarse beryl, much rifted, is found in crystals of very large size at Grafton and Acworth, N.H.; a crystal from Grafton weighing more than 22 tons . A colourless beryl from Goshen, Mass., has been called Goshenite; whilst crystals of coarse yellow beryl from Rubislaw quarry in Aberdeenshire, Scotland, have been termed Davidsonite . Beryl suffers alteration by weathering, and may thus pass into kaolin and mica . (F . W .