Fluorescence is a characteristic in a diamond that has a likelihood to project a soft colored glow when subjected to ultraviolet light (such as a "black light"). Approximately 30% of diamonds has fluoresce to some degree. Colorless (D-F) fluorescent diamonds sell at up to a 15% discount since the fluorescence is perceived as a defect. In fact, the visible effects of Faint to Medium fluorescence are perceptible only to a gemologist using a special UV light source in most cases. In some rare cases, strong fluorescence can sometimes display haziness or milky appearance in diamonds. It is always recommended to to ask your jeweler or sales professional about the appearance of a diamond before shopping if you're shopping online. It is also important take this factor into consideration while making a price comparison in diamonds.
Because the fluorescent glow is usually blue, fluorescence can make diamonds of K-M color appear up to one grade whiter. For this reason, faint yellow diamonds tend to sell at a slight premium when they possess Medium to Strong fluorescence.
Fluorescence in a diamond without a reputable laboratory certification can also be perceived as a guaranteed to be a natural diamond, as no man made stone nor lab grown diamond can have any fluorescence as this characteristic in a diamond cannot be imitated. If you are a bargain shopper, this characteristic may be very appealing to you as long as it has no effect on it's appearance. It is nearly impossible to tell fluorescence for an average consumer without using a UV light. Based on opinion it can be perceived as a positive factor for savings it can pertain, and negative to some if they want to minimize things that can affect the value of the cost of the stone.
To summarize everything, as a rule of thumb, you should always double check with your jeweler about the overall appearance of your diamond, always ask whether the diamond has any haziness of milkiness on it's appearance. Double check to make sure an apples to apples comparison is being made while shopping around, why purchase a diamond that has strong fluorescence if one with none or faint fluorescence is being offered for the same price or even less. Transparency will always avoid any returns or disappointment between the customer and the jeweler.
For any questions, please do not hesitate to reach out to us, so that we may either find you the perfect stone you are looking for or get you a better deal than the one you have already found.