People have a common misconception that diamonds sparkle like a rainbow, but in reality, they don’t.
All diamonds, however, reflect rainbows, this is known as fire and a sign of a well-cut stone. They reflect rainbow on surfaces if the lighting in the environment is right; which basically, anything that reflects light does. This means that diamonds reflect rainbows onto surfaces or objects. They do not sparkle rainbow in the stone itself. If your diamond sparkles a rainbow inside the stone, then it’s a fake diamond.
Diamonds sparkle, but it’s a gray color, not rainbow. They also come in different shades, with the rarest ones being colorless. The color of a diamond is ranked on a scale of D, which is colorless and the most expensive, to Z, which a yellowish in color.
Although recently, fancy colors are becoming more popular. Colors like yellow, chocolate, and pink, with the most saturated color being the most valuable. Nonetheless, despite colors being hard to detect once diamonds are set in a ring and placed in an environment that contains color, they do not sparkle rainbow in the stone.