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Fluorescence

Certain diamonds display a visible light when exposed to UV light. This light is known as fluorescence. For most lighting conditions, including natural light, a diamond's fluorescence will not be visible to the naked eye. However, it may release a soft colored glow if held under an ultraviolet lamp. Fluorescence is a naturally occurring phenomenon that appears in many minerals and gems. Fluorescence is categorized as None when there is no visible reaction under ultraviolet light. It will be categorized as Faint, Medium, Strong, or Very Strong depending on how much glow is observed. Fluorescence generally does not have a huge impact on a diamond’s value.