Information on gems and gemology topics



What is "Red Andesine", also known as "Red Labradorite"?

"Red Andesine" aka "Red Labradorite" is a variety of feldspar similar in composition to both Labradorite and Sunstone, but with different color and appearance, and, as recently revealed, appears to have been color-enhanced by heat or other treatments not usually applied to either labradorite or sunstone. 
The name itself can be confusing -- traditionally, "Labradorite" is the name for a phenomenal variety of feldspar originally found in Labrador.  It exhibits an iridescent, multi-colored sheen called  "labradorescense", and can sometimes also be found as cats-eye or star stones.  Generally, labradorite is not treated with heat or other enhancements.  Labradorite is one of a number of closely-related feldspars collectively known as "andesine".
Other types of andesine feldspar can be found in several colors, including the other main gem variety, "Sunstone", which is mined primarily in Oregon and has a red-orange to red color. The best sunstones have intense, striking color and show fine  needles or rays of copper called "schiller".
Within the past several years, large quantities of so-called "Red Andesine" have appeared in the gem markets and particularly on television shopping channels.  While originally promoted as a "natural" untreated gem of mysterious origin, recent gemological analysis shows that both the red and green andesine varieties that are widely sold show evidence of artificial color enhancement.  The exact form of treatment is not yet known, but may involve heat, diffusion of chemicals into the surface of  the stones, or other forms of treatment that are sometimes used to change or enhance the color and value of gemstones and gemstone rough.
Red andesine and red labradorite often show beautiful, bright colors -- but it now appears that those colors are due to enhancement, rather than being inherent to the stones themselves.