30ct Andesine (Cushion, 19.68×19.68mm, Orange) vs 30ct Benitoite (Cushion, 17.73×17.73mm, Blue)

All things being equal, Benitoite will face-up smaller than Andesine for a given carat weight, because it has higher specific gravity (3.65 vs. 2.67 - this means it's "heavier" compared to Andesine of the same size).i Face-up size also depends heavily on the proportions of the cut.

Face-up area is a measure of the size of the gem when viewed from above (as set in a ring). It tells you how big the gem is at the girdle plane.