Sunstone is a bright orange feldspar gemstone. And like most feldspars it displays on the surface of the gem. In this instance it's a brilliant, spangled effect.The optical effect of sunstone is called a shiller, and is due to the presence of copper in the mineral.
Deposits of this gemstone have been found in Norway and the United States.
On a more spiritual/metaphysical level, sunstone can be used to encourage independence and originality. It's also said to encourage good luck in games.