An enormous red jewel.
The Star Ruby, also known as Ruby, is a key item from the original Final Fantasy. It is found on the third floor of the Cavern of Earth after defeating the Vampire. Giving it to the giant in the Giant's Cave will satisfy his hunger, and he will let the Warriors of Light pass.
Asterism, or star stone, is a name applied to the phenomenon of gemstones exhibiting a luminous star-like shape when cut en cabochon. The typical asteria is the star sapphire, generally a bluish-grey corundum, milky or opalescent, with a star of six rays. In red corundum the stellate reflection is less common, and hence the star-ruby occasionally found with the star-sapphire in Sri Lanka is among the most valued of "fancy stones".