A bicolor tourmaline crystal is a single natural gemstone that displays two distinct colors within the same crystal structure. This stunning optical phenomenon occurs due to subtle environmental and chemical shifts—such as variations in trace elements like iron, manganese, or lithium—while the crystal is actively growing over millions of years.… Common Color Pairings: Pink and green (often referred to as Watermelon Tourmaline if it has a pink core and green rim), blue and green, or yellow and pink. From Afghanistan Weight : 18 grams Sizes : 12x5x5mm 21x4x4mm 17x5x4mm 17x5x5mm 15x5x4mm 11x3x3mm 13x4x2mm 14x5x5mm