Garnet is the fusion of Ruby and Sapphire and the current de-facto leader of the Crystal Gems after the previous leader Rose Quartz. Garnet is one of the last surviving Gems on Earth who joined the Crystal Gems in the rebellion against the Gem Homeworld, and afterwards assisted her friends in protecting the Earth over the next millennia. After Rose Quartz gave up her physical form to give birth to her son, Steven Universe, Garnet took over as the leader of the group. She has three eyes (usually covered by her eyeshades).

example: post #3533561 (Garnet on left)

Garnet at Steven Universe wiki: https://steven-universe.fandom.com/wiki/Garnet