noun
sapphire; jacinth
Refers to the blue gemstone sapphire. The gloss 'jacinth' is an older or poetic term for a blue gem, but in modern usage 青玉 is understood as sapphire.
See also: サファイア
彼女は青玉の指輪をはめている。
She is wearing a sapphire ring.
この青玉はとても透明度が高い。
This sapphire has very high clarity.