Natural Gemstones - Loose Precious & Semi Precious Gemstones

The Magic of Changing Colours

The most sensational feature about this stone, however, is its surprising capability of changing its colour. Green in daylight, Alexandrite changes its colour to a soft shade of red, purplish-red or purple-grey in candle light or artificial light. Thus it displays a unique optical characteristic making it one of the most valuable gemstones of all, especially in fine qualities.

Alexandrite is very scarce: this is due to its chemical composition. It is basically a Chrysoberyl, a family consisting of the colourless or yellow Chrysoberyl, Chrysoberyl Cat’s Eye and colour-changing Alexandrite. It differs from the other Chrysoberyls insofar as it does not only contain iron and titanium, but also chrome. And it is this very element which accounts for the spectacular colour-change. According to CIBJO nomenclature only Chrysoberyls displaying a distinct change of colour may be termed Alexandrite.

Its rarity is obviously caused by its formation. Like all other gemstones, Alexandrite emerged millions of years ago when the earth was still a fiery mass. It required two kinds of stone in order to create Alexandrite: one of these contributed the elements aluminium and beryllium, the other chrome. However, these conditions occurred only rarely. The result: Alexandrite crystals are very scarce indeed.

The Three Colors Of Alexandrite?

Like most other gemstones, the quality of color in alexandrite is the all-important factor. However, with alexandrite there is arguably three color factors that need to be considered within a single jewel: the daylight color, the incandescent-light color, and the degree of change between them.

Top quality alexandrite exhibits an attractive metallic bluish green color under daylight. Free from being too light, too dark, brownish or gray, the green color witnessed should be attractive within its own right.

Exactly the same principle of “attractive within its own right” should also be applied to the reddish color seen under incandescent-light. It too, should be free from being too dark, brownish or gray.

On top of these two color considerations is the degree of change experienced between the two colors – the greater the change, the more desirable the alexandrite. However, all three factors should be accounted for as a balanced sum of three parts. A striking green alexandrite that shows a vivid color change, is let down if the incandescent-light color is too dark or brown.