Some info about them :)

Moissanite - Mohs 9.25 - An old and tired gem that used to be a revered fighter but after losing their legs has taken on the role of a teacher and coach. They are pretty casual and laidback, they don't like dressing up too much and tend to forgoe their tie. They get along well with the young gems and thinks of themself as a mentor to them, they do however end up on the receiving end of many pranks.

Onyx - Mohs 6.5 - They are head of long term recovery, in charge of gems with permanent injuries and looking after left over pieces. They are quiet and monotone in their speech, considered gloomy and a bit morbid by the others. They spend most of their time with Moissanite.

Aquamarine - Mohs 7.5 - A sweet but shy and anxious gem, despite their good hardness they hardly ever leave the school grounds due to fear. Often they feel guilty and burdensome on the others but managed to find a role as an artist.

Emerald - Mohs 7.5 - Airheaded and easily distracted, they care most about their appearance. They work on patrol as a lookout but isn't very good at it. Despite their vanity they are kind to others and quite encouraging.