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From a lecture meeting of the Gemmological Society of Japan in 2006 2006.10.12
TAAFFEITE and MUSGRAVITE<GEMSTONES IN THE LATEST TOPICS>
Makoto OKANO (FGA, CGJ), Hitoshi KITAWAKI (FGA, CGJ),
Dr. Ahmadjan Abduriyim: Research Laboratory, GAAJ
  The latest topics at the GAAJ laboratory are introduced. This report is based on an oral presentation at the general lecture in the annual meeting of the Gemmological Society of Japan 2006, which was partly added and amended.

Introduction
  Taaffeite and musgravite are rare gemstones that are popular among collectors, and they are both transparent, commonly with purplish hue or rarely with slightly reddish or blueish tint
(photo 1a, b). These two gems, belonging to the same mineral group MAGNESIO TAAFFEITE, have very similar chemical composition and their properties such as RI or SG are overlapped, so that they cannot be distinguished from each other generally with standard identification tests (figure 1).
  Our study this time proved that semi-quantitative analysis using energy dispersive X-ray fluorescency (EDXRF) and Raman spectral analysis are effective to distinguish these two materials. The detail of our study is reported here.

Photo 1a:
musgravite (from left: 0.34ct, 0.40ct, 4.50ct) / courtesy of the Magical Stone Lab
Photo 1b:
taaffeite (from top left: 0.20ct, 0.39ct, 1.87ct, 1.37ct, 0.64ct; from bottom left: 0.74ct, 2.09ct, 2.19ct, 2.83ct) / courtesy of the Magical Stone Lab
fig 1F
properties of taaffeite and musgravite

Background
  Gem-quality musgravite poses a great rarity, and only eight pieces in total have been reported in gem-related documents (Schmetzer et al, 2000; 2005 a, b; Kiefert and Schmetzer, 1998) since the first appearance in 1993, and no single piece has been so far identified in Japan, to the authorfs knowledge.
  Although X-ray diffraction analysis was the only identifying method at the time of musgravitefs discovery, the powder diffraction method is a destructive test that is not an ideal way in gem identification. An effectivity of Raman spectral analysis in identification of taaffeite and musgravite was reported in 1998. As it has an advantage of non-destructiveness, this method should be highly effective in distinguishing the two materials, though, the samples supplied for testing were only in a small number and of non-gem quality, so that further examination was required.
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