Difference between revisions of "Pleochroism"

From The Gemology Project
Jump to: navigation, search
(Basic)
m
Line 1: Line 1:
 
==Basic==
 
==Basic==
  
Pleochroism is the change of color in colored anistropic ([[Double Refraction|double refractive]]) gemstones. When light enters such a gemstone it will be split in two rays that are perpendicular polarized and each of them travels at a different speed inside the gem and will therefor be refracted in different amounts.<br />
+
Pleochroism is the change of color in colored anistropic ([[Double Refraction|double refractive]]) gemstones. When light enters such a gemstone, it will be split into two rays that are perpendicular polarized. Each of the two rays travels at a different speed inside the gem, so they will be refracted differently.<br />
Both rays will experience different forces inside the gemstone which causes the light to be absorped depending on the path they travel. In other words, each ray will be absorped inside the gemstone at different amounts.<br />
+
Both rays will experience different forces inside the gemstone which cause the light to be absorbed depending on the path they travel. In other words, each ray will be absorbed inside the gemstone in different amounts.<br />
The logical consquence of this is that each ray will come out differently colored, depending on the direction. This is named "differential selective absorption".
+
The logical consequence of this is that each ray will be differently colored, depending on its direction. This result is named "differential selective absorption".
  
Sometimes one will encounter notations as "ω = dark green" and "ε = pale green". That refers to the associated colors of each ray (the ordinary ray and the extra-ordinary ray).
+
Sometimes one encounters notations such as "ω = dark green" and "ε = pale green". These notations refer to the associated colors of each ray (the ordinary ray and the extra-ordinary ray respectively).
  
Uniaxial gemstones may have two associated colors and this type of pleochroism is termed "dichroism", biaxial gemstone may have three associated colors that type is termed "trichroism".
+
Uniaxial gemstones may have two associated colors. This type of pleochroism is termed "dichroism". Biaxial gemstones may have three associated colors, and that type of pleochroism is termed "trichroism".
  
We quantify pleochroism with a few simple (self-explanatory) phrases:
+
We quantify the quality of pleochroism with a few simple (self-explanatory) phrases:
 
* Strong
 
* Strong
 
* Distinct
 
* Distinct

Revision as of 16:28, 30 November 2006

Basic

Pleochroism is the change of color in colored anistropic (double refractive) gemstones. When light enters such a gemstone, it will be split into two rays that are perpendicular polarized. Each of the two rays travels at a different speed inside the gem, so they will be refracted differently.
Both rays will experience different forces inside the gemstone which cause the light to be absorbed depending on the path they travel. In other words, each ray will be absorbed inside the gemstone in different amounts.
The logical consequence of this is that each ray will be differently colored, depending on its direction. This result is named "differential selective absorption".

Sometimes one encounters notations such as "ω = dark green" and "ε = pale green". These notations refer to the associated colors of each ray (the ordinary ray and the extra-ordinary ray respectively).

Uniaxial gemstones may have two associated colors. This type of pleochroism is termed "dichroism". Biaxial gemstones may have three associated colors, and that type of pleochroism is termed "trichroism".

We quantify the quality of pleochroism with a few simple (self-explanatory) phrases:

  • Strong
  • Distinct
  • Weak
  • None

The tool used to observe this phenomenon is the dichroscope.

Related Topics