Dawnstone

The Gems crafted from this gem match yellow sockets.

Source
This gem is mined from Fel Iron, Adamantite and Rich Adamantite deposits. It also appears to be a World Drop, most commonly reported from Solid or Bound Adamantite chests.

Dawnstone as an ingredient
Dawnstone is used in the following recipes:

Jewelcrafting

 * (requires 2)
 * Gems:

Engineering

 * (requires 2)
 * (requires 2)
 * (requires 2)

Other instances of Dawnstone

 * - a Jewel matching a yellow socket, but not crafted.