Top 10 Gemstone Special Effects Inherent In the Mineral

Metal_Treasure

The Top Ten

1 Fire Fire

It's the ability of the stone to draw light apart into its constituent colors, similarly to the glass prism.
Gems that produce the "biggest fire": diamond, zircon, benitoite and sphalerite - Metal_Treasure

2 Asterism Asterism

The ability to create a star effect - star sapphires and star rubies do it best. - Metal_Treasure

3 Schiller (Play of Color) Schiller (Play of Color)

Opals do it all the time. They just play with light and you may think that there are objects inside the gem but there aren't actual objects. - Metal_Treasure

4 Change of Color

Alexandrite is known for that - it may look green in daylight and red under incandescent light. - Metal_Treasure

5 Chatoyancy Chatoyancy

"Chatoyance" is French for cat's eye.

Chrysoberyl does it best, the variety known as Cat's Eye Chrysoberyl (in the image).
Chatoyancy is also found in Tiger's Eye. - Metal_Treasure

6 Fluorescence

The ability to turn incoming light of ultraviolet color into light of a visible color. For example, Benitoite (a blue gem) fluoresces red under long-wave UV light. - Metal_Treasure

7 Opalescence Opalescence

An effect also known as adularescence and milkiness - opal, moonstone, agate and milky quartz are the gems best known for this special effect. - Metal_Treasure

8 Labradorescence Labradorescence

It's an impressive flash of blue and golden color as the stone is moved in the light.
This effect was named for Labradorite (in the picture) - Metal_Treasure

9 Iridescence

It's a rainbow effect best displayed by fire agate and some obsidian. - Metal_Treasure

10 Aventurescence

It refers to inclusions that create internal sparkles, particularly in quartz (aventurine) - Metal_Treasure

The Contenders

11 Pleochroism

It's the ability to exhibit different colors when observed at different angles (ex., Andalusite, Iolite) - Metal_Treasure

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