There is a pearl grading system standard. Different types of pearls have different standard. So at the first you must inquire more deeply into the standards of the pearls you wanted.

s Grading

AAA:  luster : Highest ; Blemish : 95% - 100% Free ; Smoothness : Very Good ;Nacre : Thick ;

AA+:  luster : Very High ;Blemish : 90% - 95% Free ;Smoothness : Very Good ; Nacre : Thick ;

AA: luster : High ;Blemish : 75% - 90% Free ;Smoothness : Good ;Nacre : Medium to Thick ;

A+: luster : Good ;Blemish : Good ;Smoothness : Good ; Nacre : Thin to Medium ;

A:  luster : Good ;Blemish : Good ;Smoothness : Good ;Nacre : Thin to Medium ;

AAA: luster : Highest ;  Blemish : 95% - 100% Free ;  Smoothness : Very Good ;  Nacre : Thick ;

AA+:  luster : Very High ;  Blemish : 90% - 95% Free ;  Smoothness : Very Good ;  Nacre : Thick ;

AA:  luster : High ;  Blemish : 75% - 90% Free ;  Smoothness : Good ;  Nacre : Medium to Thick ;

A+:  luster : Good ;  Blemish : Good ;  Smoothness : Good ;  Nacre : Thin to Medium ;

A: luster : Good ;  Blemish : Good ;  Smoothness : Good ;  Nacre : Thin to Medium ;

A: 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 ;Pearl should drill or set clean to virtually clean Luster is very high

B: Flawless on at least 70% of pearl's surface ;Only 30% of pearl's surface may exhibit slight, concentrated imperfections ;Only one or two deep inclusions allowable; Pearl should drill or set nearly clean; Luster is high to very high

C: 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 10% of pearl's surface ;Luster is medium to very high

D: At least 60% of pearl's surface will exhibit flaws ; Deep inclusions and/or white spots within inclusions on up to 20% of pearl's surface ;Luster is poor to very high

A: 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 ; Pearl should drill or set clean to virtually clean; Luster is very high

B: Flawless on at least 70% of pearl's surface; Only 30% of pearl's surface may exhibit slight, concentrated imperfections; Only one or two deep inclusions allowable; Pearl should drill or set nearly clean; Luster is high to very high

C: 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 10% of pearl's surface; Luster is medium to very high

D: At least 60% of pearl's surface will exhibit flaws; Deep inclusions and/or white spots within inclusions on up to 20% of pearl's surface; Luster is poor to very high

When you understand the standard of the pearls you wanted, you could go to buy the pearl necklace. No matter where you want to go to shopping(online or on the jewelry shop), you should check the pearls carefully. The professional pearl's company provides free Certificate Appraisal completed by a GIA (Gemological Institute of America) graduated gemologist. Don't forget to check the certificate.

It's well-known to us that pearls of high quality should be cost a lot more than lower in quality. What you need is buy best pearls according to your budget.