Saltvandsforum.dk

The secret to the sea sapphire’s shine is in microscopic layers of crystal plates inside their cells. In the case of blue sea sapphires, these crystal layers are separated by only about four ten thousandths of a millimeter; about the same distance as a wavelength of blue light. When blue light bounces off these crystal layers, it is perfectly preserved and reflected. But for other colors of light, these small differences in distance interfere, causing the colors to cancel out. So while white light is composed of all colors, only blue light is reflected back. This type of coloration is known as structural coloration, and though resembling a gem in hue, a sea sapphire’s color has more in common with an oil sheen than a pigmented jewel. Combine this nifty trick with the sea sapphire’s impressively transparent body, and you have an animal as radiant as a star in one moment, and invisible in the next.