noun 다운로드 🔗공유 강옥 An extremely hard mineral, a form of aluminum oxide with the chemical formula Al2O3, that occurs in the form of the gemstones sapphire and ruby; it is used as an abrasive. Examples : "Because of its hardness, corundum is used in sandpaper to smooth rough wood. " 경도 때문에 강옥은 거친 나무를 매끄럽게 하기 위해 사포에 사용됩니다. mineral material geology substance chemistry science AI와 채팅어휘 게임독해 연습