Lava.

Ouranite, Uncommon

This somewhat rare ouranite is only found near active volcanoes, making it both difficult and dangerous to harvest. Harvesters should keep their eyes open and searching for runny dull red rocks floating above the lavas surface when searching for Lava Ouranite. Once processed, it takes on a deeper crimson color, gains yellow marbling, and the heat it produces is far more pronounced, often being likened to standing next to a smiths furnace, even from a short distance.

• Armor – Your armor is always pleasantly warm, even in the warmest of climates. You do not suffer negative effects of cold weather conditions, and you gain damage reduction 10 to fire damage.
• Weapon – Your weapon deals an additional 1d12 fire damage.
• Other – When activated as a bonus action, this ouranite creates a 20 ft. aura that deals 10 fire damage per round to all creatures in range. This effect may be ended as a bonus action.