They seem to be very tough and strict. They act harsh towards Phos, however, they had shown some compassion after Phos had a breakdown and had confused Cairngorm for Antarcticite. Later, Cairngorm begins to act much kinder and gentle towards Phos, and becomes rather protective of them.
When Phos lost their head to the lunarians, Cairngorm even offered their former partner, Lapis Lazuli's head, to Phos. When Kongo seemed unsure of this, Cairngorm even began to offer their own head to Phos.
Later in the manga, Aechmea questiones Cairngorm's dedication to Phos and upon examining the Gem closely, he discoveres that their eyes still contain traces of Ghost Quartz which are affecting Cairngorm's behavior. After Cairngorm breaks under Ghost's influence, Aechmea understands that Cairngorm wans Ghost Quartz removed from their eyes. With Ghost Quartz's influence removed, Cairngorm's behavior changes drastically. They remove their powder, they don't react when Phos offers to give back Lapis's head, and they refuse to join Phos' expedition back to Earth. They also seem to have formed a close relationship with Aechmea, which leads to them becoming Aechmea's "wife" during a ceremony known by the Moon People as "the wedding".