Pearl deals have been made for thousands of years, but there is no common measure yet.
Part of the problem is that there are not two pearls that are the same and that is why a complete grading system would require hundreds of quality parameters. Some gem-grade pearls are so rare that they can not be compared.
The quality-value rating measure has to do with 5 key factors that are:
Size. The pearls are measured in millimeters. Generally the bigger the pearl the more expensive it is. The dimension which is most popular today is between 61/2 and 81/2 millimeters. The measurement in a necklace is always in 2 sizes eg 7 – 71/2, meaning all the pearls of the necklace range from 7 to 71/2 mm and this is because of their uniqueness.
Shape. The more rounded, the more symmetrical pearl is the most expensive. Baroque pearls that are asymmetrical, may be shiny and beautiful but often cost less than round.
Surface. The perfect pearl should be without any sign, protrusion or cracking. The more signs and spots it has, the more its value falls.
Colour. Pearls are made in various colors from pink to black. The color is purely personal silver-pearl taste best suited to light-colored skins, as well as creamy and golden pearl shades fit in dark skins. We recommend Imperial White as a perfect color with a slightly pink color.
Shine. The combination of the surface of the pearl gloss and the depth of polishing. High quality pearls must be open, dazzling and can reflect any object near them.