Ignium

Ignium is a rare ore which only forms in areas surrounding volcanic activity and within the Elemental Plane of Fire. Ignium retains it heat when smelted and forged into armour, weapons, and other objects.
In its raw form ignium appears much like bright burning coals. When forged ignium appears like fire, white-yellow at its centre fading through orange and red, before it reaches black along its edges.