Jacinth

Unique to the Realms, jacinth, also known as hyacinth and flamegem, was a corundum gemstone similar to sapphire.

Description
This rare jewel had a fiery orange hue and was as hard and durable as sapphire and ruby. Each stone had a heart of fire that flickered like a candle&mdash;bright enough to be seen in the dark but not enough to illuminate even nearby objects. This property made it highly prized for adornment on cloaks and gowns worn by the well-to-do. A typical specimen had a base value of 5,000 gp

Powers
Powdered jacinth was used in potions and in the immersions used for the creation of magic items that provided protection against fire. Whole jacinths were used in the ornamentation of such devices, e.g., a ring of fire resistance.