HYACINTH, or JACINTH  , in mineralogy, a variety of zircon (q.v.) of yellowish red colour, used as a gem-stone . The hyacinthus of ancient writers must have been our sapphire, or blue corundum, while the hyacinth of modern mineralogists may have been the stone known as lyncurium (AuyKOU;iiov) . The Hebrew word leshem, translated ligure in the Authorized Version (Ex. xxviii . 19), from the X yuprov of the Septuagint, appears in the Revised Version as jacinth, but with a marginal alternative of amber . Both jacinth and amber may be reddish yellow, but their identification is doubtful . As our jacinth (zircon) is not known in ancient Egyptian work, Professor Flinders Petrie has suggested that the leshem may have been a yellow quartz, or perhaps agate . Some old English writers describe the jacinth as yellow, whilst others refer to it as a blue stone, and the hyacinthus of some authorities seems undoubtedly to have been our sapphire . In Rev. xx . 20 the Revised Version retains the word jacinth, but gives sapphire as an alternative . Most of the gems known in trade as hyacinth are only garnets—generally the deep orange-brown hessonite or cinnamon-stoneand many of the antique engraved stones reputed to be hyacinth are probably garnets . The difference may be detected optically, since the garnet is singly and the hyacinth doubly refracting; moreover the specific gravity affords a simple means of diagnosis, that of garnet being only about 3.7, whilst hyacinth may have a density as high as 4.7 . Again, it was shown many years ago. by Sir A .

H .

Church that most hyacinths, when examined by the spectroscope, show a series of dark absorption bands, due perhaps to the presence of some rare element such as uranium or erbium . Hyacinth is not a common mineral . It occurs, with other zircons, in the gem-gravels of Ceylon, and very fine stones have been found as pebbles at Mudgee in New South Wales . Crystals of zircon, with all the typical characters of hyacinth, occur at Expailly, Le Puy-en-Velay, in Central France, but they are not large enough for cutting . The stones which have been called Compostella hyacinths are simply ferruginous quartz from Santiago de Compostella in Spain . (F . W .