jacinth in early use, a gem of a blue colour, probably a sapphire, mentioned in Exodus 28:19 as being in the high priest's breastplate, and in Revelation 21:20 a stone in the wall of the New Jerusalem; the name comes (in Middle English) from an Old French or medieval Latin alteration of Latin hyacinthus ‘hyacinth’. In modern usage, jacinth denotes a reddish-orange gem variety of zircon.

Jacinth

A gemstone, a variety of zircon that was believed to protect the wearer from plague and from lightning, to strengthen the heart, and to bring wealth, honor, prudence, and wisdom. It was recommended by Albertus Magnus as a soporific on account of its coldness and was ordered by Psellus in cases of coughs, ruptures, and melancholy; it was to be drunk in vinegar. Marbodeus described the wonderful properties of three species of jacinth. Pliny and Leonardus also spoke highly of it.

jacinth XIII. ME. iacin(c)t — OF. iacinte (mod. jacinthe), or medL. iacintus, L. hyacinthus HYACINTH.

ja·cinth / ˈjāsən[unvoicedth]; ˈjas-/ • n. a reddish-orange gem variety of zircon.