Phenomena Gems
Phenomenal gems are gems that show unusual optical effects caused by reflection, interference and refraction usually from oriented inclusions. For example, the play-of-colour in opal is caused by interference, others like star ruby, star sapphire, cat’s eye chrysoberyl are caused by the internal reflection of needle-like inclusions, etc.
Other phenomena gems include color change garnet, alexandrite, moonstone, opal, hackmanite, chameleon diamonds!
