Jacinth - Vine's Expository Dictionary of New Testament Words
Jacinth[ A-1,Noun,G5192, huakinthos ]
primarily denoted a hyacinth," probably the dark blue iris; then, "a precious stone," most likely the sapphire, Revelation 21:20.
[ B-1,Adjective,G5191, huakinthinos ]
signifies "hyacinthine," perhaps primarily having the color of the hyacinth. Some regard its color as that of the martagon lily, a dusky red. According to Swete, the word in Revelation 9:17 is "doubtless meant to describe the blue smoke of a sulphurous flame."