Color
- The primary consideration is the extent of color change. The most desirable color change is saturated ruby red (incandescent lighting) to saturated emerald green (day light or fluorescent light). Quite often the stones have color modifiers which may result in the reds having a purplish, and the greens a bluish secondary color.
- In most cases the saturation level of both hues is relatively low so stones that show colors of high intensity fetch higher premium.
Phenomenon
- The stone should display distinct change of color from an incandescent light source to a day light fluorescent one.
Clarity
- The clarity of the stone is a factor. Alexandrites may be heavily included; as long as the inclusions are not too distracting, the stone should be judged based on the unique color change.
Cut
- Alexandrites are usually faceted. If they a show a chatoyant phenomenon, they may be cut cabochon.
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