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Color of Jewel

   Last Modified:    Published: 2021/04

Color of Jewel

As a charm point of Jewelry, a number of colors are available. There are two basic colors: one is Idiochromatic and another Allochromatic. The idiochromatic is a color achieved by the main “ingredients” which form the jewel. The allochromatic is a color made with impurities.
For example: although corundum is originally water-clear, when iron and titanium are added, blue sapphire is made.
Moreover, if chromium goes into corundum, the result will be a ruby, but it becomes pink sapphire when chromium is less than 1%. Blue diamond is boron into carbon.

Change of Color with Impurity


There are some gemstones with their color differing depending on the viewing angle. This property is called pleochroism. This is because the character changes with the viewing direction of the crystal. The absorption band of the wavelength of light changes by the direction of light going through. Moreover, there are also some gemstones of which color may differ depend on the light source. This calls "allochroism." Alexandrite becomes red under a filament lamp and green under natural light.

How to investigate a streak color should rub jewelry against the white streak plate. Instead of a streak plate, you may use rim of the bottom a tea cup or the back side of a tile.

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