Before buying a diamond ring, it helps to know the Four Cs—cut, color, clarity,...

https://atomic-wiki.win/index.php/What_Labs_Besides_GIA_Grade_Diamonds_and_How_Do_I_Choose%3F

Before buying a diamond ring, it helps to know the Four Cs—cut, color, clarity, and carat—to understand what you’re getting. Check for a GIA grading report number to verify quality