You are given two crystals. One crystal is a yellow

You are given two crystals. One crystal is a yellow diamond that has been kept locked in a freezer for 30 years. The other crystal is a cubic zirconia. Both are virtually the same hardness. What simple test could you perform to tell them apart? What mineral group would a diamond be classified as? Lastly, would you settle for a blue cubic zirconium rather than a yellow diamond? Defend your reasoning.