Ruby has light bright red skin, dark maroon hair, and is slightly taller than Steven. She wears a maroon and red-violet tank top, a red-violet headband around thick fluffy, outgrown hair cropped at the neck, mid-thigh length burgundy shorts, and short pointed red-violet boots.
She embodies Garnet's strength and courage, contrasting Sapphire, who embodies Garnet's cool nature and kindness. She seems to put the well-being of Sapphire over all else, as she immediately made sure Sapphire was safe and responded "Who cares?!" when Sapphire asked her if she was okay. She also seems to not be very conversant, a trait which she carries onto Garnet, as Ruby mumbles and speaks somewhat awkwardly. She is shown to be very hot-heated, and has a very short temper. When she is angry enough, she can go into a rampage. She seems to be very dramatic as well, even referring to herself as an "eternal flame". Ruby also places much value in trust and fusion, being absolutely outraged with Pearl when she learned she was tricked.
Unlike Garnet, Ruby doesn't possess future vision. Joe Johnston confirmed that when she complained about not being able to "see" (use future vision), it was because she was so used to having that second sight while being fused with Sapphire. This meaning that Sapphire is the one that has future vision, as is shown in "Keystone Motel".
- Super Strength: Ruby seems to possess a higher degree of strength than most Gems, as she was able to shake the walls of her prison with a single punch and lift Sapphire with little effort in "Jailbreak", and flip a diner booth with relative ease in "Keystone Motel".
- Thermo-regulation: Ruby is able to increase her core temperature. This is shown in Keystone Motel when her body gets so hot that it begins burning the carpet of the motel room, and when she boils a pool to nothing but steam in a very short amount of time. It is unknown if she can decrease her temperature, though.
You know what's nice about being split up? I get to look at you.
|—Ruby, in "Keystone Motel"|
The episode "Keystone Motel" reveals that their relationship can be strained at times due to Sapphire's Future Vision causing her to be preoccupied with the outcome of events, instead of the events as they happen. This puts her at odds with the passionate Ruby who very much lives "in the now". In said episode, Ruby was furious over Pearl's deception in "Cry For Help" but Sapphire wasn't because she had seen that in the future they would all get along again - this greatly irritated Ruby as she felt that Sapphire was acting cold, emotionless and distant.
At first Ruby seemed cold and distant towards Steven due to wanting to find Sapphire as quickly as possible. Despite this, Ruby cares deeply for Steven evident by trying to tell him not to put his hand through the force field for his own safety. Also Garnet says that both her and Sapphire had already loved Steven when he asked if he made a good first impression. She was also upset by the fact that their plan of revealing themselves on Steven's birthday had failed, apparent when she said to Steven, "Oh great! This is just perfect! and "Don't look at me." When Steven became upset because Ruby and Sapphire were arguing Ruby and Sapphire came to his aid showing how much she cares.
Pearl and Amethyst have been aware of Garnet's true identities for several millennia. Their perception of the two while separated remains unknown, but given their good relationship with Garnet it can be assumed it is a positive one.
Upon encountering The Cluster, Ruby and Sapphire were both disturbed to the point of almost defusing. While Ruby reacted with the most verbal anger and outrage at what Homeworld had done to their fallen friends, it was Garnet's right eye that represents Ruby that started crying indicating that she was deeply saddened as well. From their own comments, as well as that of Garnet herself, it can be assumed that they knew the individual members of The Cluster.
- "Fusion Cuisine" (brief cameo)
- "Jail Break" (debut)
- "Love Letters"(mentioned)
- "Keeping it together" (mentioned and talking as garnet)
- "Keystone Motel"
- Garnet and the other Crystal Gems had planned to wait for Steven's birthday to introduce Ruby and Sapphire to him.
- It is unknown whether or not they will still do this.
- Although she was not formally introduced until "Jail Break," her silhouette, along with Sapphire's, can be seen when Alexandrite unfuses in "Fusion Cuisine." To the left of "Garnet" is seen as Ruby, and to the right of "Garnet" is seen as Sapphire.
- Ruby and Sapphire are lovers, as shown by Ruby's desperate desire to find Sapphire, and the kiss that is part of their fusion dance. It also explains why they chose to stay as their fusion, Garnet. 
- Most of Garnet's sensitive side seems to come from Ruby; whenever Garnet cries, her tears fall from her right eye, the red-colored one, that represents Ruby. Also, Ruby cried when she and Sapphire met again in "Jail Break", while Sapphire herself appeared to remain calm.
- When asked if Ruby was blind from when she says "I can't see", Joe Johnston merely stated that she was "used to being fused with Sapphire, and so, used to having two types of vision." 
- Ruby is the birthstone of the creator of Steven Universe, Rebecca Sugar.
- Ruby and Sapphire both lack stars on their outfit.
- It was revealed in "Love Letters" that her and Sapphire's relationship was a gradual building up over-time.
- It's possible that Ruby and Sapphire both have rooms in the Crystal Temple, due to the fact that they both have their corresponding gemstones on the door.
- Ruby's gemstone location is not symmetrical, along with Sapphire's.
- When fused as Garnet, however, their combined gemstones become symmetrical.
- Ruby is the second shortest Gem, the shortest being Steven.
- However, she is the shortest pure Gem, given that Steven is half-human.
- She and Sapphire talk to each other individually through Garnet in "Keeping it Together" and "Keystone Motel."
- Ruby and Sapphire are both named after varieties of corundum (crystalline aluminum oxide, chemical formula Al2O3).
- In the extended theme song, Ruby is shown to be cracking or holding her knuckles, a sign of toughness, anger, or that she's ready to fight, while Sapphire is holding her hands together, interlocking her fingers. This shows that she is calm, graceful and passionate.
- Ruby is one of three Gems to have made the most fusions, four, (Garnet, Sugilite, Alexandrite, and Sardonyx); Sapphire and Pearl are the other two Gems to have made four fusions.
- Ruby's gauntlet resembles the superhero Hellboy's stone fist.
- Ruby is a gemstone of emotion, associated with passion, strength and anger. This shows in Ruby's emotional temperaments and overall emotional/angry attitude, as well as her strength when she shakes her cell and lifts Sapphire.
- Ruby is the birthstone for those born in July, and is also the zodiacal stone for Cancers.
- Ruby is a variety of corundum that gets its red color from chromium.
- The vivid red color of ruby also means that it is associated with desire, and it is thought by some to be a stone of love with an aphrodisiac effect.
- Ruby is considered as one of the four precious gemstones, together with sapphire, emerald, and diamond.
- Ruby's chemical formula is Al2O3::Cr+3, where chromium, as an impurity, make rubies take an intense red coloration.
|Ruby's gemstone is located on the palm of her left hand, and has a square facet. As seen in "The Return" and the flashback in "Jailbreak", it has a light pink ring around the edge (normally hidden inside her hand), and is flatter on the back.|