Taaffeite / Musgravite Info

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General and History

Despite its color taaffeite is a rare, most required, very expensive, transparent, mauve (usually) gemstone, first thought to be a mauve spinel. It belongs to the mineral group magnesio taaffeite. It was named after Count Edward Charles Richard Taaffe (1898-1967). Taaffe was a keen gemologist who discovered the mineral in October 1945 when he inspected a "spinel" from a lot of gemstones which were broken from old jewelry. Taaffe wanted to buy these stones (zircons, opals, garnets, citrines, amethysts, spinels, rubies, emeralds, and sapphires) from his Irish jeweler friend Robert Dobbie.
One stone showed a strong double refraction, sank in methylene iodide, and Taaffe came to the conclusion that it couldn't be a spinel. Then he sent it to B. Anderson (London Chamber of Commerce) who identified the stone as a new mineral. This very rare occasion, that a new mineral was discovered from a faceted stone, let collectors inspect their spinels to find out if one of their stones may be a taaffeite. But taaffeite is so rare that another stone was dicovered not until 1949. Until 1980, 10 stones were discovered, and until 1983, a maximum of 50 taaffeites were known worldwide.
Until 2004 the crystal system of taaffeite was unknown. Then a perfect crystal was found in Sri Lanka.

Resources

The taaffeite discovered by Count Taaffe was from Sri Lanka, as most taaffeites. Then, in 1963, Peng Zhizhong and Wang Kuiren ("The crystal structure of taaffeite" - Scientia Sinica, 1963, Vol.12, No.2, pp 276-278) described a taaffeite paragnesis from the Chinese Xianghualing Mine / Xianghualing ore field / Linwu County / Chenzhou Prefecture / Hunan. Chinese taaffeite is of some lower grade, associated with fluorite.
In 1977, more taaffeite was found in eastern Siberia (in limestone - granite contact), followed by taaffeites from Australia (Mount Painter Provice / South Australia) in 1980, 1983 from Myanmar, and 1996 from Tanzania.
In Sri Lanka taaffeite is found in alluvial deposits (as water worn pebbles). Therefore the original geologic origin is still unknown. In other deposits taaffeite is found in amphibole, granite or metamorphic lime stone (e.g. in China where taaffeite occurs in limestone dolomite in contact with granite).

Color and Transparency

Best taaffeite is transparent with no inclusions. Taaffeite colors vary from white to violet, rarely showing a reddish or blue tint. Most taaffeites are pale mauve. Mauve stones are colored by iron, purple or purple-red stones are colored by chrome. Deep purple or red taaffeites are very rare and come from Sri Lanka.

Distinguishing between Taaffeite and Musgravite

Though taaffeite is very rare, musgravite is even rarer. Both minerals belong to the same mineral group "magnesio taaffeite". They have similar chemical compositions and cannot be easily distinguished from each other. Taaffeite is magnesiotaaffeite-2N'2S, musgravite is magnesiotaaffeite 6Ní3S (formulas: see our taaffeite page).
Musgravite was discovered in 1967, at Ernabella Mission / Musgrave Ranges / South Australia. The mineral was associated with spinel, sapphire and phlogopite. It seemed to be a variation of taaffeite but was finally identified as a new mineral and a new, extremely rare gemstone. Only complicated investigations in laboratories (using X-ray fluorescency (EDXRF) and Raman spectral analysis) can distinguish taaffeite from musgravite. After the first discovery of musgravite, taaffeite collectors rushed to laboratories in order to test their taaffeites. From 1993 until 2000, only two (greenish gray) musgravites, probably from Sri Lanka, were identified. Until 2006, about 20 fasceted musgravites were identified, three of them by the Canadian gemologist Murray Burford. Since 2005, musgravite was found in Antarctica (Casey Bay), Greenland, Madagascar, Sri Lanka, and Tanzania.
Taaffeite can be colorless, pink, purple or reddish. Musgravite is pale olive-green.

Differences between taaffeite and musgravite:

Formula: Taaffeite: BeMg3Al8O16, Musgravite: Be(Mg,Fe,Zn)2Al6O12

Crystal system: Taaffeite: Hexagonal, Musgravite: Trigonal

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