Yes, there are naturally occurring blue diamonds. Blue diamonds are among the rarest and most highly sought-after gemstones in the world. The Natural Blue Diamond is caused by the presence of boron impurities during the diamond's formation process. The amount of boron present determines the intensity and shade of blue in the diamond.

Blue diamonds can range in color from light blue to deep blue, and they are graded based on factors such as hue, tone, and saturation. The Gemological Institute of America (GIA) uses a grading scale that categorizes blue diamonds as Fancy Light Blue, Fancy Blue, Fancy Intense Blue, and Fancy Vivid Blue, with Fancy Vivid Blue being the most vibrant and valuable.

Notable blue diamonds include the Hope Diamond, the Blue Moon Diamond, and the Blue Heart Diamond. These diamonds are famous for their exceptional size, color, and historical significance. However, due to their rarity, natural blue diamonds are incredibly expensive and highly coveted by collectors and enthusiasts.