Fluorescence: The Hidden Light in Colored Gemstones

Fluorescence is a fascinating phenomenon that adds an unexpected dimension to the beauty of diamonds and gemstones. This effect is an optical reaction that occurs when a gem absorbs UV light and releases it as visible light. It can manifest in various shades, ranging from blue to yellow, green, or even red, depending on the gem’s chemical composition. The type and intensity of fluorescence can vary greatly from one stone to another, even within the same type of mineral.

In diamonds, fluorescence is a relatively common feature: about 30% of diamonds exhibit some degree of fluorescence. The most common hue is blue, which becomes visible when the diamond is exposed to UV light. This reaction can have an interesting impact on the diamond’s appearance, as a diamond with moderate blue fluorescence can appear "whiter" or even brighter, especially in diamonds with slightly lower color grades (such as J, K, and L).

However, very strong fluorescence can have a negative effect, making the stone appear slightly milky or hazy, even in natural light. For this reason, fluorescence is carefully evaluated and reported in gemological certificates, as it can influence the diamond’s value.

In addition to diamonds, many gemstones exhibit interesting fluorescence, which can enhance their beauty and uniqueness. For example, some rubies may display intense red fluorescence, making their hue even more vibrant, even in natural light. Sapphires can show a blue fluorescence that enhances their color depth. Other gems, such as spinels and certain varieties of garnet, can also display notable fluorescence, adding an extra dimension to their aesthetic. Opals often exhibit green or blue fluorescence, which accentuates their play of colors, creating an almost hypnotic effect.

The value of fluorescence in gemstones is a matter of perception and personal preference. For some collectors, slight fluorescence is a desirable feature, while in other cases, particularly with diamonds, strong fluorescence diminishes the stone’s transparency and brilliance. Understanding the role of fluorescence and knowing how to appreciate it can help make more informed choices when purchasing jewellery, turning each piece into an even brighter living work of art.