GARNET

From Agepedia

GARNET ; one of the most beautiful species in mineralogy, whether we consider the perfection of its crystallizations, its varieties of colors, or the degree of lustre and transparency which its individuals often possess. When in distinct crystals, it generally assumes the form of the regular dodecahedron, which is its primitive form. It is sometimes truncated upon all its edges, by sixsided planes, which, when produced so as to obliterate the primary faces, convert the crystal into the trapezohedron, which is a frequently occurring form in the species. Another very frequent form is that of the dodecahedron, with all its edges bevelled. The general aspect of its crystals, even when perfect, is somewhat spherical, on account of the great number of their sides. It sometimes occurs in fragments or grains, and in amorphous masses, either lamellar or granular. Its varieties are not all equally hard. They, however, strike fire with steel, and scratch quartz. Its structure is seldom distinctly foliated. Its fracture is uneven, or more or less conchoidal, and its lustre, though variable in degree, is usually vitreous, sometimes resinous. Its specific gravity extends from 3.55 to 4.35. It sometimes moves the magnetic needle; indeed, most of its varieties, when examined by double magnetism, affect the needle. Its prevailing color is red of various shades, but it is often brown, and sometimes green, yellovy or black. It is usually translucent, sometimes transparent, and not seldom opaque. It is easily melted by the blowpipe into a dull, black enamel, which is often magnetic. The essential ingredients of the garnet are probably silex, alumina and lime. The numerous varieties in character presented by that group of minerals, at present united within the species garnet, render it probable that the species will, hereafter, be found to admit of several divisions. The limits of hardness and specific gravity are wider than we are accustomed to observe in one and the same species. A variety of distinctions among the contents of the species have arisen out of accidental circumstances, for the most part; yet, as they are in common use, they require to be hinted at here. Grossular is of a gooseberrygreen color, and crystallized in the ordinary forms of the species; it occurs in Siberia. Pyreneite occurs in small blackish crystals, imbedded in a darkcolored limestone, and hitherto found in the French Pyrenees. Melanite is of a perfectly black color, and generally crystallized in dodecahedrons, with their edges truncated. It is found in a volcanic rock near Vesuvius, but in the most beautiful groups near the Franklin furnace in Hamburg, New York, in a white limestone rock. Pyrope occurs only in grains, and is remarkably distinct by its pure translucency and bloodred color. It is found in Bohemia and some other countries, in alluvial deposits, accompanied by hyacinths and sapphires. Pre£wus Garnet is always red, and its crystals are found imbedded in various forms. Its most remarkable localities in the U. States, are Hanover, New Hampshire, where it occurs in very perfect dodecahedral crystals, in hornblende gneiss; Haddam, Connecticut, where it accompanies chrysoberyl in granite; and Franconia, New Hampshire, where it is found along with magnetic iron ore. Precious garnet is found in foliated masses in Greenland, of a deep bloodred color, and also occurs at Fahlun in Sweden, in very large, but not transparent crystals, often covered with a coat of chlorite. Fine specimens are found in Ceylon, Pegu, Brazil and Bohemia ; indeed, it occurs in most countries. It is translucent, and often transparent, but frequently impure at the centre. This variety is found both in primitive and secondary rocks, and sometimes in alluvial earths. The term Oriental, sometimes applied to this variety, indicates not a locality, but merely a great degree of perfection. The precious garnet, and the species called pyrope, are employed in jewelry, for broaches, ringstones, necklaces, &c. The carbuncle of the ancients was probably a garnet. According to Pliny, it was sometimes formed into vessels capable of containing nearly a pint. In the national museum at Paris is a head of Louis XIII, engraved on a garnet. Common garnet seldom occurs in red colors, and these are of dirty shades. Its crystals are generally implanted. Its localities are too numerous to be enumerated. Colophonite is a compound variety of yellowish brown and reddish brown, or honeyyellow colors, consisting varying from hyacinthred to < low. It is both crystallized am In the latter condition, it has be from Ceylon, where it is fou sand of rivers. The crystalliz have been found in Massachusi lisle, in white limestone, and near Bath. The following show the composition of ga principal varieties: GrossutMdanl Free 'Catop lar. | ite. \ious G.\ onit 144.00 8.50 133.50 12.00 [35.50 6.00 132.50 124.25.40 135.75 27.25 36.00.25 37.C 13i 29.C 11 4.1 Silica, Alumina, Lime,Ox. of Iron,Ox. of Manga.) The common garnet may tageously employed as a flu ores. The powder of the gar in polishing hard bodies, and is called red emery.