Fluorescence: Hidden Light

Fluorescence is a fascinating phenomenon that adds an unexpected dimension to the beauty of diamonds and coloured gemstones. This effect is an optical reaction that occurs when a gemstone absorbs UV light and re-emits it as visible light. It can display in various shades, from blue to yellow, green, or even red, depending on the gemstone's chemical composition. The type and intensity of fluorescence can vary widely between stones, even within the same mineral type.

In diamonds, fluorescence is relatively common, with about 30% showing some level of fluorescence. The most common hue is blue, which becomes visible when the diamond is exposed to UV light. This reaction can positively influence the appearance of a diamond; for example, a diamond with moderate blue fluorescence may look “whiter” or even more brilliant, especially in slightly lower colour grades (such as J, K, and L).

However, very strong fluorescence can have the opposite effect, causing the stone to appear somewhat milky or hazy, even in natural light. For this reason, fluorescence is carefully evaluated and recorded in gemological certificates, as it can affect the diamond’s value.

Beyond diamonds, many gemstones exhibit intriguing fluorescence that can enhance their beauty and uniqueness. Some rubies, for instance, display intense red fluorescence, making their colour appear even more vibrant under natural light. Sapphires may exhibit a blue fluorescence, which enhances their depth of colour.

Other gemstones, such as spinels and certain varieties of garnet, can also show strong fluorescence, adding extra visual appeal. Opals often display green or blue fluorescence, accentuating their colour play and giving an almost hypnotic effect.

The value of fluorescence in gemstones largely depends on personal perception and preference. For some collectors, a subtle fluorescence is a desirable trait, while in other cases, particularly with diamonds, strong fluorescence can diminish a stone’s transparency and brilliance.

Understanding the role of fluorescence and knowing how to appreciate it can help buyers make more informed choices when purchasing jewellery, transforming each piece into a radiant, living work of art.