When I taught optics at the University of California, Berkeley, I enjoyed making this point, and bringing in large (several centimeters in size) cubic zirconias cut in the classic shape of diamonds.

Ettika Treasure Emerald Cut Cubic Zirconia Band Ring ($40) For a diamond engagement ring that'll never go out of style, we'd go with this emerald cut cubic zirconia pick from Bloomingdale's.

The Alice Cubic Zirconia Ring still grabs all the attention, especially now that it’s 25 percent off. Alice Cubic Zirconia Ring. $19, originally $48. Buy now Maro Ring Set. Image: BaubleBar.