|For other uses, see Onyx (disambiguation).|
|For other uses, see Quartz (disambiguation).|
You don't need to be like Bradford. You're perfect just being you. We all love you because you're you. I love you because you're you.
|—Amethyst to Onyx, "Onyx Shapes Up", Crystal Island Adventures|
In Onyx's first speaking role, he asked Bradford to teach him how to control the trucks, which ended up causing trouble for Amethyst in the end. Amethyst then told him that he should be himself and not try to be like Bradford.
Amethyst later said that Onyx became upset when Quartz pulled Pink apart. The two best friends then got into a fight over it because Amethyst didn't think it was a big deal, while Onyx thought the exact opposite. However, after spending a week with Lapis, Onyx reconciled with Amethyst and the two have since been inseparable.
Onyx and Amethyst later explained to the Off Colors that they are defective. The two offer the explanation that Amethyst should be larger and Onyx should be an engine like their Keystone Railway counterparts
Onyx is quiet and kind, but also gets very upset if someone disagrees with him.
Onyx is based on a Great Western Railway 16-ton brake van. Early vans were just 10 or 16 tons weight, but this gradually increased to 20 and 25 tons. Toad is also based on one of these brake vans.
Onyx is painted gray. he has his name on his side in black. he also has a black gem and roof.