Article in English: Most diamond retailers hire their own gemologists and appraisers, but many consumers find it more desirable to request third party appraisal from an independent gemologist who specializes in the appraisal of diamonds. If you're going to invest in a stone, or are curious about a stone you already own, you'll want to be sure that the stone you've got is appraised accurately.  An appraisal involves two basic steps: first identifying and evaluating the stone in question, and then assigning value. When looking at independent appraisers, it would be ideal to select an appraiser with a Graduate Gemologist (GG) degree issued by a Gemological Institute in your country, who isn't involved directly in the sale of diamonds. This way, you can be sure that the science is sound. Aside from finding out whether or not the stone is fake, a good appraiser can answer a variety of questions about the quality of your stone to make sure that you're not getting ripped off. This is especially important if you've already purchased or inherited a stone. The gemologist should be able to tell you:   whether or not the stone is man-made or natural (Note: man-made diamonds are diamonds, just not "natural". See the section on detecting man-made diamonds for more detail.) whether or not the stone has been color-altered whether the stone has had permanent or temporary treatment added whether a stone matches the grading documentation provided by a retailer Whatever tests you choose to have performed, the best and most reliable way to tell if a diamond is real is to check the paperwork and speak to the gemologist or the appraiser. Certification and grading assures you that your stone has been "proven" real by experts. Proof is especially important if you're buying a stone sight-unseen, like from the Internet. Ask for a certificate. The certificate should be from a grading authority (e.g. GIA, AGSL, LGP, PGGL) or an independent appraiser who is affiliated with a professional organization (like the American Society of Appraisers) but not with any...

Summary in Vietnamese:
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