**Hardness**: 10 One of the gems who focuses on patrol duty. Despite their high offensive power, their toughness is second-rate and easily broken. The other gems consider them lovely and a top fashion model. Diamond has a clear, colorless scheme yet their gem's characteristic gives them high light dispersion, thus creating rainbow reflections. They are very sparkly and blinding. They sparkle and glow even during the night, though they seem to be able to dampen it by covering part of it up. Their hair is a fluffy short-medium bob, with thick eyebrows and eyelashes. They wear either a winter or summer uniform depending on the season. They also wear standard black shoes with small bows. Like a diamond, they always wore white opera gloves with thigh-high socks.

Spoiler

On the Moon, they wear feminine and frilly outfits that often resemble dresses with puffy skirts.

Diamond is very friendly, kind, and gentle. They appear to be relatively calm during a battle, even when their situation isn't good. However, they are actually insecure and frustrated with their current body which, though being the hardest, shatters easily. They dislike being compared to Bort, although they admire their younger sibling a lot. They are perceptive regarding gems' inner feelings and relationships, though Cinnabar accuses them of seeing everything as some kind of romance. Despite their more gentle nature, they're very stubborn and tend to fight until they shatter in battle. From Bort's point of view, Diamond is extremely reckless.

Spoiler

When separated from Bort on the Moon, Diamond seems to display fear at the mention of Bort, signifying that there was more hostility in treatment from Bort towards Diamond and their feelings. Phosphophyllite eventually uses this to take advantage of Diamond in threatening to bring Bort to the Moon so they comply in assisting with destroying the Earth gems. Diamond mentions that they would like to turn that "little nuisance (Bort) into dust". Invading Earth proper, Diamond is immediately angry at Bort for their unwillingness to fight and their kindness towards Cinnabar. When they're able to shatter them, Diamond is darkly satisfied with their pyrrhic victory even as both Bort and Diamond fall to pieces.

(Source: Houseki no Kuni Wiki, edited)