Yellow Diamond

"Yellow Diamond" was first mentioned in "The Return".

Jasper/Peridot/Lapis Lazuli
Yellow Diamond seems to hold some sort of authority, as Jasper and Peridot needed to report to her. As they seem to obey her, Lapis Lazuli and Peridot feared her name.

In "Cry for Help", Peridot sent out a distress signal using the Communication Hub in hope that Yellow Diamond would send help.

Appearances

 * "The Return" (mentioned)
 * "Cry for Help" (mentioned)

Trivia

 * To date, Yellow Diamond has been mentioned twice, the most recent in "Cry for Help".
 * In a San Diego Comic-Con clip, a silhouette of an unknown Gem can be seen alongside Jasper, Peridot and Lapis. This was later confirmed to be Yellow Diamond by Steve Wolfhard via Twitter post.

Gemology
Gemstone Information
 * Diamonds are the stones of truth and victory.
 * Diamond is the transparent, gemstone-quality crystalline form of carbon and it is indeed the hardest known natural substance on earth.
 * Diamonds are typically known to be colorless or 'white', but the most common colors are yellow and brown.
 * Red diamonds are actually one of the rarest gemstones in the world.
 * Diamond is the official modern birthstone for April, and it is also used as an official sixty year anniversary gemstone.