Houseki no Kuni

is a manga written and illustrated by Haruko Ichikawa. It runs in Kodansha's Monthly Afternoon magazine. It is published in English by Kodansha Comics.

Plot
In the distant future, a new life form of non-gendered beings called the Gems are born. The 28 Gems must fight against the moon dwellers called Lunarians who want to attack them to bring them back to the moon and turn them into decorations, and thus each gem is assigned a role such as a fighter or a medic. Phosphophyllite is the youngest and most fragile of all the gems, and wishes to be assigned the role of a fighter. Though because of how fragile and clumsy they are, they have yet to be assigned any role. But one day the gems' master, Kongo-sensei, is finally ready to assign Phos a job and asks them to create an Encyclopedia of their natural history.

Official

 * Official Anime Website
 * Official English Manga Website