Gemstone Effects


The ability of the stone to draw light apart into its constituent colors. (Seen in diamonds).

Schiller or ‘Play of Color’

Interior of stone shows flickers of color when it is moved in the light. (Seen in opals.)


Ability of stone to turn ultraviolet light into visible color.  (Seen in some diamonds and rubies)


A flash of blue and golden color when the stone is moved in the light. (Seen in Labradorite).

Change of color

Appearing as different color in different lights. (Seen in Alexandrite and some tourmalines.)


Rainbow effects, includes schiller and labradorescence. (Seen in mother-of-pearl and some agates and obsidian).

Opalescence / Adularescence / Milkiness

Subtle iridescence caused by scattering of light.  (Seen in opal, moonstone, some agate and milky quartz).


Inclusions that create internal sparkles. (Seen in quartz / aventurine).

Chatoyancy / Cat’s Eye

A bright reflective line in the stone. (Seen in Tiger’s Eye, Cat’s Eye).


When the cat’s eye effect shows in two or three directions at once. (Seen in star sapphire / corundum).

Sources / further reading:


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