Sugilite is colossal. She features four, medium-lilac eyes located under a strong brow and a fifth one above it. Her mouth is twisted into a grin and filled with sharp, pointed teeth. She has a giant plume of spiky, dark purple-black hair kept in an untamed style similar to Amethyst's, but messier. Her skin color is lavender, like Amethyst's. She appears to have purple fingernails painted to appear as gems themselves.
Her gemstones are located on her chest, and on the palms of the hands of her upper arms. As of Amethyst and Garnet's regenerations, Sugilite's palm gemstones have been relocated.
Sugilite cares for herself first and foremost. Though she carries out mission objectives effectively, she has problems with impulse control and does not hesitate to use her power for personal gain. She combines Garnet's headstrong, unwavering nature with Amethyst's indulgence, as well as her negative attitude towards authority. The resulting personality is a volatile mix that is highly aggressive and dangerous to everyone she encounters. This causes at least one perilous situation, wherein Sugilite, enraged that she was left behind during a mission and asked to unfuse, viciously attacks and severely injures Pearl. She seems to possess some of Ruby and Sapphire's feelings towards separating. She also appears to be cold like Sapphire can be, containing Ruby's anger issues and Amethyst's recklessness. All of Sugilite's constituent Gems contribute to her general temperament, though the similarity in nature of Amethyst and Ruby seemingly eclipse Sapphire.
Despite her destructive nature, she does seem to retain an attachment to Steven, refraining from marking him as a direct target during her rampages. Ironically, she inadvertently causes a chunk of debris to fly off at Pearl, who deflects it and hits Steven in the face. Sugilite appears to want to impress Steven with her strength, asking if he wanted "to see something cool?" when summoning Garnet's gauntlets and Amethyst's whip to form her flail.
Sugilite possesses standard Gem abilities, bubbling, shapeshifting, fusion, regeneration, agelessness, and superhuman strength/durability.