Idiochromatic vs Allochromatic Gems
With regard to the source of their color, gems fall into two categories: idiochromatic and allochromatic. Idiochromatic gems derive their color simply from the chemistry of their basic formula.
Idiochromatic
Gems
The colors in these idiochromatic gems come from elements that are an essential part of their chemical composition. These gems generally have only one color, or show a very narrow range of colors.
Idiochromatic
Describes gems whose colour is due to elements that are an essential part of the chemical composition.
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1. Idiochromatic Coloration in Gemstones
Minerals that are "self-colored" from major chemical constituents (chromophores) that are key components in their physical makeup.
Idiochromatic staurolite develops in regional metamorphic rock formations. In petrology, it is used as an index mineral to define the grade and type of the host rock. Staurolite rarely occurs in massive form.
Idiochromatic...Minerals...in which the color is due to an essential constituent.
Igneous rock.. Rock formed by the solidification of magma.
icosi-tetrahedron Synonym of trisoctahedron idiochromatic Exhibiting only a single color. Minerals that are monochromatic occur in only one color, no matter what specimen. Same as monochromatic. igneous Of volcanic origin.
This type of coloration in minerals is termed idiochromatism; different samples of an idiochromatic mineral species will all display the same color. Other minerals are colored by the presence of certain elements in mixture.
This makes it an idiochromatic stone - colored by itself. The green color arises from iron in the olivine, the actual name of the mineral. Peridot measures 6.5 on the Mohs hardness scale, making it a relatively soft stone that is easy to cut.
In regards to coloring agents, minerals are termed idiochromatic (self colored) if the color results from an element that is a basic part of the mineral’s chemical formula.
 See also: Color, Gemstone, Mineral, Stone, Minerals
  
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