noun🔗Share刚玉 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."Because of its hardness, corundum is used in sandpaper to smooth rough wood. "由于刚玉非常坚硬，所以常被用于制作砂纸，用来磨平粗糙的木头。mineralmaterialgeologysubstancechemistryscienceChat with AIVocabulary GamePractice Reading
