The chemical formula of sapphire (Ruby) is:
- AAl2O3
- BAl3O2
- CN2O
- DNO2
- ENone of the above/More than one of the above
Show answer and explanation
Correct answer: (a) Al2O3
Explanation
Sapphire and ruby are both forms of the mineral corundum, which is aluminium oxide, Al₂O₃. Traces of other metals give the colour: chromium makes ruby red, iron and titanium make sapphire blue.
Corundum is the second hardest natural mineral after diamond, 9 on the Mohs scale.