Andesine

Name and discovery

Andesine was first described in 1841 for an occurrence in the Marmato mine, Marmato, Cauca, Chocó Department, Colombia. The name is for the Andes due to its abundance in the andesite lavas in those mountains.

In the early 2000s, red and green gemstones began to be marketed under the name of 'andesine'. After some controversy, these gemstones were subsequently discovered to have been artificially-colored.

Occurrence

Andesine occurs in intermediate igneous rocks such as diorite, syenite, and andesite. It characteristically occurs in metamorphic rocks of granulite to amphibolite facies commonly exhibiting antiperthite texture. It also occurs as detrital grains in sedimentary rocks. It is commonly associated with quartz, potassium feldspar, biotite, hornblende, and magnetite.

Andesine controversy

In the early 2000s, a new variety of red or green gemstone resembling sunstone and called "andesine" appeared in the gem market. After much controversy and debate, most of these gemstones, allegedly sourced from China, were subsequently discovered to have been artificially colored by a copper diffusion process. A Tibetan source of bona fide (untreated) red andesine, however, was eventually verified by a number of independent groups of well-respected gemologists.

References

References

1. [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Andesine Mineralienatlas]
2. [http://rruff.geo.arizona.edu/doclib/hom/andesine.pdf Handbook of Mineralogy]
3. [http://webmineral.com/data/Andesine.shtml Webmineral data]
4. [http://www.mindat.org/min-220.html Mindat.org]
5. Klein, Cornelis, and Cornelius S. Hurlbut, Jr., ''Manual of Mineralogy,'' Wiley, 20th ed. 1985, p. 455 {{ISBN. 0-471-80580-7
6. Tables of Gemstone Identification By Roger Dedeyne, Ivo Quintens p.118
7. "Three Occurrences of Oregon Sunstone | Gems & Gemology".
8. "Three occurrences of Oregon sunstone".
9. Huges, Richard W.. (14 November 2011). "Tibet andesine mines; Part 2". RWH Publishing.
10. Huges, Richard W.. (3 November 2010). "Tibet's andesine mines {{grey". RWH Publishing.
11. Abduriyim, Ahmadjan. (10 September 2009). "A mine trip to Tibet and Inner Mongolia: Gemological study of andesine feldspar". [[Gemological Institute of America]] in Thailand (GIA Thailand).
12. (2009). "The characteristics of red andesine from the Himalaya Highland, Tibet". [[The Journal of Gemmology]].
13. (2008 <!--). "Visit to andesine mines in Tibet and Inner Mongolia; Gemological properties of andesine collected in Tibet and Inner Mongolia". [[Gems & Gemology]].