Alexandrite is the fusion of Garnet (and, by extension, Ruby and Sapphire), Amethyst, and Pearl. She made her debut in "Fusion Cuisine"
Role in the series
Alexandrite starts off cold, somewhat distant, intense, and sloppy. As the fusion becomes more unstable, the Crystal Gems' individual personalities become more prominent, showing Pearl's fear of food, Amethyst's hunger and argumentative personality, and Garnet's social awkwardness, leadership, and control of situations.
During "Fusion Cuisine" she is not shown to have her own personality, but rather three separate personalities, each one being that of Garnet, Amethyst, and Pearl. These personalities can exist at the same time and come into conflict with each other, causing Alexandrite to defuse.
As shown in "Super Watermelon Island", she is able to keep herself together when in serious situations. She is seen to be a ferocious fighter, roaring in a bestial-like manner before charging at her enemy. However, she offers to settle things peacefully before the battle, reminding her enemy that they don't have to fight.