Jacinth

Jacinth is a precious stone whose name marks a deep blue or smoky-blue hue. The UPDV preserves the term in two Revelation passages — once in the older spelling "hyacinth," describing the color of breastplates in a vision of cavalry, and once as "jacinth" naming one of the twelve foundation stones of the New Jerusalem.

Hyacinth in the Cavalry Vision

The sixth-trumpet vision of horsemen pictures their breastplates in three colors, the second of which is rendered as the gemstone hue: "having breastplates [as] of fire and of hyacinth and of brimstone: and the heads of the horses are as the heads of lions; and out of their mouths proceeds fire and smoke and brimstone" (Rev 9:17). The triplet — fire, hyacinth, brimstone — pairs the smoky blue of the stone with the red of fire and the yellow of brimstone, matching the smoke-and-flame imagery that closes the verse.

The Eleventh Foundation Stone of the New Jerusalem

In the catalogue of foundation stones for the wall of the New Jerusalem, the same gem stands eleventh in order: "the fifth, sardonyx; the sixth, sardius; the seventh, chrysolite; the eighth, beryl; the ninth, topaz; the tenth, chrysoprase; the eleventh, jacinth; the twelfth, amethyst" (Rev 21:20). The stone closes a sequence of color-rich gems and is set just before amethyst — placing the deep blue of jacinth alongside the violet of amethyst at the end of the twelve-stone foundation.