Opal

Opal is the fusion of Pearl and Amethyst. She made her debut in the episode "Giant Woman".Amethyst's ability to live in the moment and Pearl's obsessive single-mindedness results in a stable fusion. Opal achieves a sense of peace in that balance that Amethyst and Pearl rarely experience on their own. At times, she is so calm and at peace that she forgets the task at hand like forgetting to retrieve the Heaven Beetle after rescuing Steven. According to the book Guide to the Crystal Gems, Opal is very forgetful.
Opal's personality is theorized to be a combination of Amethyst's carefree personality and power, along with Pearl's grace and precision. She appears to be more open to Steven's desire to have fun and play, as she sang part of his song back to him. In "Fusion", Opal shows posed with elegant and silly poses.
The balance that holds Opal together is, by far, the thinnest of all the other known fusions. In the "Fusion" short, she is referenced as an example of how fusion is hard for Gems who have trouble collaborating. The ease with which she can separate is very different from that of Garnet, who only involuntarily unfuses when under extreme emotion or by force. If Pearl and Amethyst have conflicting views while fused, Opal may revert to her constituent Gems; the slightest dissonance between the two poses a danger of involuntary defusion.[​1] In "Log Date 7 15 2", Amethyst and Pearl are shown to have a much easier time fusing than before.