Phosphophyllite

Phosphophyllite, usually called Phos, is the youngest gem at the beginning of the story and has a hardness of 3.5. Weak, brittle and clumsy, they are ill-suited to combat or most duties despite wanting to be useful. Their first assignment is creating a natural-history encyclopedia, and they also promise to help Cinnabar find a better role.

Phos is overconfident, naive and willing to talk back to Kongou. Other gems often call them lazy or useless, comments that appear to affect their self-esteem even as they continue trying to help.