Jacinth (ja'-sinth) is a red transparent variety of zircon used as a gemstone. Jacinth is also a flower of a reddish blue or deep purple (hyacinth), and hence a precious stone of that colour (Revelation 21:20).
It has been supposed to designate the same stone as the ligure (Hebrew leshem) mentioned in Exodus 28:19 as the first stone of the third row in the high priest's breast-plate, the Hoshen. or choshen. In Revelation 9:17 the word is simply descriptive of colour.
Read more about Jacinth: Use in Literature