An engagement ring in itself is a prized possession but when it’s an alexandrite engagement ring it becomes even more valuable due to the rarity of the gemstone which is fondly called ‘chameleon of all gemstones’ due to its color-changing properties. Here Step-by-Step Guide Before Buying Alexandrite Engagement Ring Color Change Color is the primary driver of value in the case of color gemstones . If the color is vivid and the saturation is high, the gemstone is valued highly.