Iridescent stone

OPAL

This gem is often associated with October births and can display a play of colors that shifts with the angle of light.

The clue "Iridescent stone" points to opal because opals are famous for their shimmering, rainbow-like play of colors. The word "iridescent" directly describes this unique optical effect, where light bends and reflects in shifting hues. No wordplay is involved—it’s a straightforward definition matching the gemstone’s most distinctive trait.