For strongly pleochroic gems like ruby, tanzanite, and tourmaline, the
manufacturer usually positions the rough crystal to show the most attractive
pleochroic color in the finished gemstone. That’s because a
pleochroic gem that displays its most attractive color well is worth
more than one that doesn’t. For example, sapphire’s pleochroic colors
are violetish blue and greenish blue. Cutters usually fashion rough
sapphires to emphasize the violetish blue color because sapphires with
greenish color are less valuable