This new gem is known by the mineralogists but is very rare in agem quality.
We present on this website the new discovery from the Democratic Republic of Congo in 2002.
Andesine belongs to the group of plagioclase feldspar
Since its discovery in the area of Goma, no other Andesine coming from the DRC has been available in the gem market.
Andesine is an intermediate member of the plagioclase series, close to the Labradorite. The name depends of the ratio of Sodium and Calcium between Albite (Na(AlSi3O8) and Anorthite (Ca(Al2Si3O8). The stones examined by different laboratories have shown less than 50% of Calcium, thereby entitling them to be called Andesine
A lot of analysis from different well known gemological laboratories and institutes have been done (AGTA-USA / Nantes University - France / CCIP - France / JGGL - Japan / AIGS - Thailand / Smthsonian Institute in Washington - USA).
And our 57 largest stones underwent chemical analysis by the AIGS.
All of these stones were confirmed to be Andesine. And all these analysis have never shown any indication of treatment.
The red color of the Andesine is due to copper. Their clarity is exceptional. Red feldspar gemstones are extremely rare. The most well known was the Labradorite from Oregon, also called “Oregon Sunstone”, but these are never found in sizes as large or in colors as red as this new discovery. The Congo Andesine contains more copper than the Oregon Sunstone.
Only a few hundred flawless "top red" stones were cut, and we have almost all of the world stock of this Congo Andesine. There has been no further Andesine from this source offered on the market since we purchased these stones. We have also other Andesine that has an orange-red or orange color in a lower price range. You may find other Andesine on the market with an orange color and/or visible inclusions in an even lower price range, however we do not carry stones in this lesser quality.
A few rare specimens from the same source are yellow or green, and a few have an “alexandrite effect” color change (green / red, yellow/red).
Since 2002, another discovery said from China has produced Andesine of lesser quality than those from the Congo. But further investigatins have shown that these "andesine" was coming from yellow labradorites bought in Mexico and treated...
Another new source was also said coming from Tibet in 2005.
_ The "Chinese Andesine" (also called "Tibet Sunstone" or "Tibet Andesine") on the market is not as pure, and the red stones appear to have a brownish tone that is not present in the Andesine from our inventory. We also noted that the "Chinese Andesine" has a "sleepy" appearance compared to the stones found in the Congo.
After the 2006 Tucson gemshow (USA), we can confirm that the availability of high quality stones will remain weak. Even if another deposit of Andesine should be discovered, this gem will still remain much rarer than a diamond!
Like Tanzanite, Andesine has a hardness of 6.5 (Mohs scale), and is therefore suitable for jewelry. Unlike Tanzanite, these stones are not heated or enhanced in any way.
The bright beautiful red color is as it came from the earth, and not induced by heat treatment, as is almost always the case with Tanzanite.
In addition, Andesine is considerably rarer than Tanzanite ; compare the few hundred stones of Andesine found to date to the ten of thousands of Tanzanites.
To learn more about the mineralogy of the andesine, see Mindat.org
To see our andesines on sale->
