Some precious stones such as ruby and sapphire consist of aluminum oxide coloured by traces of the oxides of

Some precious stones such as ruby and sapphire consist of aluminum oxide coloured by traces of the oxides of

Answer Details

Precious stones such as ruby and sapphire consist of aluminum oxide (Al₂O₃) colored by traces of transition metal oxides. The transition metal ions, such as chromium (Cr) and iron (Fe), replace some of the aluminum ions in the crystal lattice of the aluminum oxide, and give the stones their characteristic colors. For example, chromium gives rubies their red color and iron gives sapphires their blue color. Therefore, the correct option is "transition metals".