When sourcing saltwater pearls (such as Akoya, Tahitian, or South Sea), you must evaluate the '5 S's' of pearl quality: Size (measured in millimeters, where even 0.5mm significantly impacts price), Shape (perfectly round commands the highest premium), Surface (cleanliness and absence of pits or bumps), Shine/Luster (the sharpness of reflections on the surface), and Shade/Color (body color plus 'overtone'). For B2B buyers, nacre thickness is a critical technical spec; for Akoya pearls, a nacre thickness of ≥0.5mm is preferred for long-term durability.