Red Orange Zircon from Tanzania
Jacinth is a traditional term for yellow, orange or red-brown zircon. Though the term jacinth is no longer much used in the gem trade, it is an important part of the history of gemstones. It dates back to the one of the most important historical gemstone references, the description of the breastplate of Aaron in the Old Testament:
"And you shall make a breastpiece of judgment, in skilled work; like the work of the ephod you shall make it; of gold, blue and purple and scarlet stuff, and fine twined linen shall you make it. It shall be square and double, a span its length and a span its breadth. And you shall set in it four rows of stones. A row of sardius, topaz, and carbuncle shall be the first row; and the second row an emerald, a sapphire, and a diamond; and the third row a jacinth, an agate, and an amethyst; and the fourth row a beryl, an onyx, and a jasper; they shall be set in gold filigree. There shall be twelve stones with their names according to the names of the sons of Israel; they shall be like signets, each engraved with its name, for the twelve tribes."(Exodus 28:15-21)
Orange Zircon from Cambodia
No one is sure exactly which gem jacinth referred to, since at that time there was no science of mineralogy and gem names were really only color descriptions. But the color of jacinth is believed to be orange or red, since the name derives from the Latin hyacinthus, referring to the flowering plant still known today as hyacinth. Hyacinth occurs in a number of colors, including red, blue, white, orange, pink, violet and yellow.
It is not really known how the name jacinth came to refer to the orange or red zircon. Zircon gems were certainly well known in classical antiquity, and the orange, orange-red and brown-red colors for gems are not that common in the gems world. Today we recognize a number of gems in that color range, including sapphire, spessartite garnet, fire opal, hessonite garnet, citrine and sphalerite. But none of these were as well known as zircon in the ancient world.