Phosphophyllite (フォスフォフィライト, Fosufofiraito), or Phos for short, is the main protagonist and the youngest Gem in anime and manga series Houseki no Kuni (宝石の国, Hōseki no kuni). They're weak, brittle - not suited for battle - and their clumsiness makes them difficult to maintain any other roles. Phos has always wanted to be useful.
Phos' initial job was to make a natural history encyclopedia which they progressed very little on. They promised to help Cinnabar find a job suited for them as well.
Phos so far is the only Gem who has had drastic body and personality changes.