Color is the most visible and important factor when considering the value of Alexandrite. The most sought after color combinations are gemstones that display a true bluish-green hue under daylight equivalent lighting and a vibrant reddish-purple hue under incandescent lighting.
There is a dramatic rise in value for 'eye clean' gemstones as visible inclusions will affect the light inside the gemstone and impair the color change. Currently, the mines in Brazil are yielding some of the cleanest specimens of Alexandrite found on Earth.
The highest quality Alexandrite is most commonly fashioned in what is a called a 'mixed cut.' This cut allows for a larger table and steeper cut pavilion to maximize the weight, preserve the color saturation and color-change. Fancy shapes are incredibly rare to find as it is more difficult to cut while maintaining the quality of the color-change.
Typically, the value of a colored gemstone is predominately determined by its size, however, with natural Alexandrite, we buy for color-change. A large portion of the very limited supply received from the Brazilian mines are under 0.25 ct. when rough. This means that the largest category of faceted Alexandrites are between 0.09 ct. to 0.14 ct. Stones over 0.75 ct. that meet the strict quality control requirements are extremely difficult to obtain. Increasingly fewer stones over 1.00 ct. are available each year.