In the 35.00+ carat size range, carat weight and rarity become the most important value factors. Often the proportions or cut will be less than ideal – as achieving ideal proportions would result in too much carat weight loss.
Tanzanites over 50.00 carats are often very dark – almost navy blue to blue black in color. Tanzanite this size is almost exclusively graded with a tone and saturation above the 6/6 listed as optimal for stones under 30 carats. This is often a combination of their large size ,which is naturally able to “hold” more color and deeply cut pavilions (undersides)