Fel Iron Ore

Fel Iron Ore is mined from Fel Iron veins, with a minimum mining skill of 275.

Source
Fel Iron Deposits are found throughout Outland.

Fel Iron Deposits are by far most commonly found in Hellfire Peninsula. They are also fairly commonly found in Zangarmarsh, Terokkar Forest, and Nagrand, but do appear elsewhere.

Fel Iron Ores can also be found by fishing Heavy Supply Crate in Zangarmarsh.

5x Ores are also rewarded in Outland Sucks! (quest)

Also found in Fel Iron Veins

 * (1-4) Mote of Fire (12%)
 * (1-4) Mote of Earth (12%)
 * Eternium Ore (1.2%)

The following gems may also be found while mining Fel Iron Veins. Collectively, a gem appears about 3% of the time.
 * Deep Peridot
 * Blood Garnet
 * Shadow Draenite
 * Flame Spessarite
 * Azure Moonstone
 * Golden Draenite
 * Living Ruby
 * Noble Topaz
 * Star of Elune
 * Dawnstone
 * Nightseye
 * Talasite

Smelting (Mining)

 * Smelt fel iron - requires mining skill 275

Prospecting (Jewelcrafting)
Fel Iron Ore can be prospected by Jewelcrafters with a skill of 275, resulting in:
 * Deep Peridot
 * Golden Draenite
 * Flame Spessarite
 * Azure Moonstone
 * Blood Garnet
 * Shadow Draenite
 * Nightseye
 * Living Ruby
 * Dawnstone
 * Talasite
 * Noble Topaz
 * Star of Elune

As a quest objective

 * Outland Sucks! (quest)
 * 5 Fel Iron Ore is part of the reward.