(hyʹa·cinth).

A deep-blue semiprecious stone; in Greek, hy·aʹkin·thos. (Primarily the word referred to the flower by that name, probably describing the dark-blue iris.) The 11th of the foundation stones of New Jerusalem is said to be hyacinth.​—Re 21:20.

Hyacinth blue (hyacinthine) is one of the colors of the breastplates in the description of the armies of cavalry, at Revelation 9:16, 17. The breastplates spoken of were probably those worn by the riders of the horses. Fire red and sulfur yellow are mentioned as the other two breastplate colors. In view of the later statement that the horses breathed out fire, smoke, and sulfur, the hyacinth blue may represent the darkness of smoke, which, along with fire and sulfur, may be destructive to life.