IRIDESCENT RAINBOW GARNETS FOR SALE

What Causes The Iridescence?

The vibrant color play in iridescent garnets arises from the way light interacts with microscopic structures inside the crystal. In many specimens, ultra-thin lamellar bands—minute internal layers only hundreds of nanometers thick—act like natural diffraction gratings, splitting incoming light into shifting rainbow hues. The spacing and orientation of these layers determine whether a crystal shows a soft metallic sheen or intense, prism-like flashes. In other garnets, alternating layers of slightly different composition produce thin-film interference, where light reflecting from each boundary overlaps to create vivid, iridescent colors. These effects are exceptionally rare in the garnet family, forming only under very specific geological conditions involving precise chemistry and slow cooling, as documented in well-known occurrences such as Nara in Japan and the Fem-minutter’n locality in Norway.