An Introduction to Gemstone Grading

Step 4: Gem Grading

Lesson 1

gemstone grading - diamonds and colored gems
Although gemologists look at color, clarity, cut, and carat to evaluate both diamonds and colored gems, they must judge these qualities in the stones very differently. “Emerald Ring,” 750-White gold, Colombian emerald, and diamonds, by Mauro Cateb. Licensed under CC By 2.0.

The Diamond Four Cs Standard

Until the 1930s, no standards for gemstone grading existed. When the Gemological Institute of America (GIA) instituted the four Cs method for grading diamonds, it revolutionized the industry. This method became the standard we still use today. Prior to this, individual dealers set their own standards. One might grade diamonds as A, B, and C, while another would grade them AAA, AA, and A. In this case, the second dealer’s A grade equaled the first’s C grade. You can imagine the confusion. Standardization was a boon to both the public …

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