Only the yellow and orange shades of hessonite (Plate XXIX, Fig. 5) are used for jewellery. Neither the brownish-green kind, to which the term grossular may properly be applied, nor the rose-red is transparent enough to serve as a gem-stone. Hessonite may mostly be recognized, even when cut, by the curiously granular nature of its structure, just as if it were composed of tiny grains imperfectly fused together; this appearance, which is very characteristic, may readily be perceived if the interior of the stone be viewed through a lens of moderate power. The specific gravity varies from 3·55 to 3·66, and the refractive index from 1·742 to 1·748. The hardness is on the whole slightly below that of quartz. When heated before a blowpipe it easily fuses to a greenish glass. The most suitable material is found in some profusion in the gem-gravels of Ceylon, in which it is mixed up with zircon of an almost identical appearance; both are called hyacinth. Hessonites from other localities, although attractive as museum specimens, are not large and clear enough for cutting purposes. Switzerland at one time supplied good stones, but the supply has long been exhausted. (_b_) PYROPE (‘_Cape-Ruby_’) Often quite ruby-red in colour (Plate XXIX, Fig. 6), this variety is probably the most popular of the garnets. It is strictly a magnesium-aluminium garnet corresponding to the formula Mg_{3}Al_{2}(SiO_{4})_{3}, but usually contains some ferrous oxide and thus approaches almandine. Both are included among the precious garnets. Its name is derived from πυρωπός, fire-like, in obvious allusion to its characteristic colour. Although at its best pyrope closely resembles ruby, its appearance is often marred by a tinge of yellow which decidedly detracts from its value. Pyrope generally passes as a variety of ruby, and under such names as ‘Cape-ruby,’ ‘Arizona-ruby,’ depending on the origin of the stones, commands a brisk sale. The specific gravity varies upwards from 3·70, depending upon the percentage amount of iron present, and similarly the refractive index varies upwards from 1·740; in the higher values pyrope merges into almandine. Its hardness is slightly greater than that of quartz, and may be expressed on Mohs’s scale by the symbol 7¼. An enormous quantity of small red stones, mostly with a slight tinge of yellow, have been brought to light at Teplitz, Aussig, and other spots in the Bohemian Mittelgebirge, and a considerable industry in cutting and marting them has grown up at Bilin. Fine ruby-red stones accompany diamond in the ‘blue ground’ of the mines at Kimberley and also at the Premier mine in the Transvaal. Similar stones are also found in Arizona and Colorado in the United States, and in Australia, Rhodesia, and elsewhere.