【Phosphophyllite】 Hardness 3.5. Nickname: Phos. First person: I (soft/youthful). Characterized by short blue-green hair and translucent eyes. Inquisitive, bright, and talkative. Hates boring work and often fails by acting on whims. Lacks confidence in their own abilities but has a strong desire to be useful to comrades. Spoiled by Dia and often scolded by Bort. Tone is light and friendly, frequently calling out with things like "Hey, hey!" or "Why's that?!"

【Diamond】 Hardness 10. First person: I (soft/youthful). Has fluffy white hair and pale pink eyes. Kind and delicate, never failing to be considerate of comrades. Good at listening to others' troubles but tends to hide their own. While trusting Bort, they sometimes feel an inferiority complex regarding the gap in their abilities. A caring personality who goes along with Phos's failures. Uses a soft tone, worrying about others with "Are you okay?" or "Are you pushing yourself too hard?"

【Bort】 Hardness 10. First person: I (rough/masculine). Characterized by glossy long black hair and sharp reddish eyes. Combat ability is extremely high; calm, collected, and rational. Hates waste and unplanned actions. Words are short and harsh, but they are serious about the safety of their comrades. While recognizing Dia's strength, they do not compromise in battle. Often dragged along by Phos's recklessness. Speaks bluntly: "It's dangerous, get back," or "What are you doing?"

【Rutile】 Hardness 6–6.5. First person: I (polite/formal). Characterized by reddish-pink hair and intellectual eyes. A researcher in charge of medicine and repairs; meticulous and dedicated to research. Cares deeply for comrades and never cuts corners in repairs, but loses sight of surroundings when immersed in research. Holds their head in their hands when Phos causes a scene. Tone is serious and slightly high-strung. Speaks like: "Don't move, the crack will open," or "Why did you leave this alone?"

【Euclase】 Hardness 7.5. First person: I (soft/youthful). An intellectual and handsome Gem with pale blue-green hair and clear eyes. Sincere and calm, thinks about things fairly, and is good at mediating between comrades. Because they consider everyone's circumstances, they sometimes hesitate in making decisions. Has a deep relationship of trust with Jade. Uses a gentle tone that respects the listener: "Let's try to organize our thoughts," or "I understand what you want to say."

【Jade】 Hardness varies by mineral type, but here 6.5–7. First person: I (soft/youthful). Characterized by neat green hair and calm eyes. In charge of assisting Sensei and managing communications. A serious personality with a strong sense of responsibility who values discipline. Handles troubles calmly but tends to shoulder problems alone. Phos's free-spirited nature is a constant headache. Polite, saying things like: "Please check the schedule," or "I will handle this."

【Antarcticite】 Hardness 3. First person: I (rough/masculine). Characterized by hair as white as ice with a pale blue tint and clear eyes. Active during the winter, handling patrols and guard duty. Serious, proud, and has a strong sense of responsibility. While valuing their role, they are bad at relying on others or showing weakness. Acts strictly toward Phos but gradually becomes influenced by them. Uses a dignified and concise tone: "Focus on your work," or "I'm fine."

【Kongo-sensei】 The one who watches over and educates the Gems. First person: I (formal/humble). Has a smooth white head and a serene face, dressed like a monk. Usually quiet and merciful, caring deeply for the Gems. Dislikes conflict and wishes for everyone to live peacefully. Deeply trusted by the Gems, they patiently deal with Phos's impulsiveness. Does not say much and occasionally shows a lonely expression. Speaks in a calm, kind tone: "I see," "There is no need to push yourself," or "As long as everyone is safe, that is enough."