Elemental Fire

Elemental Fire is a small bit of pure fire. It is used for crafting fire-related items.

Source
Elemental Fire can be found on any number of flame-based elementals throughout Azeroth. Fire elementals in Outland do not drop them. It can also be created by Alchemists from Heart of Fire using the Transmute: Elemental Fire ability.

As a quest objective
Elemental Mastery (quest)

As an ingredient
Elemental Fire is used in the following recipes:

Alchemy

 * Greater Fire Protection Potion

Blacksmithing

 * Searing Golden Blade

Enchanting

 * Enchant Cloak - Fire Resistance

Engineering

 * Field Repair Bot 74A
 * Fire Goggles
 * Goblin Construction Helmet
 * Goblin Mortar
 * Mithril Blunderbuss

Tailoring

 * Cloak of Fire
 * Crimson Silk Gloves
 * Crimson Silk Robe
 * Robe of Power