irridescence

The luminous property of pearls, whereby their layers of nacre splits white light into its component colours giving their surface a shimmering or irridescent appearance
Found on http://www.saffronart.com/sitepages/jewelry/glossary.aspx

Irridescence

This is an optical phenomenon in which the hue on the surface of the stone changes according to the angle from which the surface is viewed. A similar phenomenon may be seen on the surface of soap bubbles and on butterfly wings. The word is derived in part from the Greek word iris, meaning 'rainbow', from the goddess Iris, the personification of the...
Found on http://www.braybrook.co.uk/jewellery-and-silver-wisdom/gems-of-information/
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