The Crystal of Air, or Air stone, was one of the three Stones of Power that, when united, created the Crystal of Knowledge. It was a silver fragment with the Kryptonian symbol for "Air", and the symbol of The House of El.

The Crystal of Air was hidden in Shanghai, East China on the planet Earth by a Kryptonian centuries prior to its discovery in 2005. The stone was inside a statue of a horse that was buried under a tree near a temple in China.

In 2005, Lana Lang went to China, searching for the Crystal of Air. She was captured and tortured by Chinese officers, causing Isobel to emerge. She found Crystal of Air but was confronted by Clark Kent and reverted back to Lana after they battled.

Months later, Genevieve Teague confronted Lana, demanding she hand over the Crystal of Air. They struggled, and when Genevieve began to strangle Lana, Isobel emerged once more. She used the Air stone to stab Genevieve in the chest, killing her. Because the crystal was stained with human blood, Isobel’s link to Lana was broken. However it also activated the Black Ship and the Disciples of Zod, causing the ship to arrive on Earth along with meteors, which fell on Smallville.

Lana gave the stone to Clark, who united it with the Crystal of Fire. Once united, the two crystals revealed to Clark the location of the Crystal of Water. He combined all three stones and created the Crystal of Knowledge.