MIRA Grading system
A-D system and the A-AAA system
Top gem quality
Gem Grade Flawless pearl with excellent luster
Pearl exhibits no inclusions or imperfections prior to setting or drilling
A | AAA
Flawless on at least 90% of pearl's surface
Only 10% of pearl's surface may exhibit slight, concentrated imperfections
Only a single deep inclusion allowable
Luster very high to excellent*
A/B | AA+
Flawless on at least 80% of pearl's surface
Only 20% of pearl's surface may exhibit slight, concentrated imperfections
Only one or two deep inclusions allowable
Luster is high to very high*
B | AA
Flawless on at least 70% of pearl's surface
Only 30% of pearl's surface may exhibit slight, concentrated imperfections
Few inclusions allowable
Luster is medium to high
C | A+
Flawless on at least 40% of pearl's surface
Up to 60% of pearl's surface may exhibit slight, concentrated imperfections
Deep inclusions are limited to pearl's surface
Luster is low to medium
D | A
At least 60% of pearl's surface will exhibit flaws
Deep inclusions and/or white spots within inclusions on pearl's surface
Luster is poor