Gem Phenomena is the observed effects of light interacting with the gem stone.
The phenomena appear different from gem type to gem type and only rarely appear.
The gem phenomena make the particular gem a sort after collectors item.
There are many types of gem phenomena, below is a list of the most popular.
- Adularescence - a cloud like affect that almost seems to float in mid air, found in feldspar.
- Asterism - meaning star is caused by intersecting rutiles or very thin inclusions.
Commonly seen in sapphire, ruby and garnet.
- Aventurescence - flat inclusions within the gem stone give rise to this type of sparkle.
The color of the sparkle depends on the type of the inclusion. ie. mica, copper, hematite etc...
Aventurine quartz and aventurine feldspar are the most common type of gem to exhibit this phenomena.
- Chatoyancy - commonly known as cats eye is the result of light refracting of needle inclusions (known as rutiles),
like asterism except they point in only one direction.
- Color Change - some gems change color when exposed to different lights.
This is caused by the gems shape that causes part of the crystal to absorb light differently from other parts.
Most of these types of gems can display two colors, some can display any of three different colors.
Alexandrite is the best known color change gem.
- Color Play - this is caused by the light diffracted off tiny silica particles within an opal.
The most sort after color play is red fire against a black back drop.
- Iridescence - This is the display of rainbow like colors in feldspars.
It is caused by the interference with light as it enters the stone and encounters inclusions.
This type of gem is generally either cut flat or rounded and polished to take full effect of this phenomena.
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