• journal_title：European Journal of Mineralogy
• Contributor：Xiande XIE ; Michelle E. MINITTI ; Ming CHEN ; Ho-Kwang MAO ; Deqiang WANG ; Jinfu SHU ; Yingwei FEI
• Publisher：E. Schweizerbart'sche Verlagsbuchhandlung Science Publishers
• Date：2003-
• Format：text/html
• Language：en
• Identifier：10.1127/0935-1221/2003/0015-1001
• journal_abbrev：Eur J Mineral
• issn：0935-1221
• volume：15
• issue：6
• firstpage：1001
• section：Articles

Tuite, γ-Ca₃(PO₄)₂, the high-pressure polymorph of whitlockite, was found in a shock melt vein of the Suizhou chondrite. It occurs as polycrystalline aggregates in association with coarse-grained aggregates of ringwoodite, majorite and NaAlSi₃O₈-hollandite. These high-pressure mineral assemblages are enclosed in the fine-grained matrix of the vein that consists of majorite-pyrope_ss garnet, metal and troilite. This new mineral is trigonal, R3̄m,a = 5.258 Å, c = 18.727 Å. The tuite is colourless and transparent with vitreous lustre and white streak; it is uniaxial (+) with high refractive indices (ϵ = 1.706, ω = 1.701) and low birefringence (0.005). Microprobe analyses of tuite yield an empirical formula (Ca_2.51Mg_0.29)_2.80Na_0.28(P_1.01 O₄)₂. The simplified formula, Ca₃(PO₄)₂, is the same as whitlockite outside the veins. Stronger reflections on synchrotron radiation X-ray powder diffraction pattern of tuite are d = 2.628 (100), 2.891 (80), 1.945 (47), 1.730 (25) and 1.567(22). The figures in brackets are relative intensities. Tuite in the shock vein of this meteorite was transformed from whitlockite via a shock-produced solid-state reaction, while the pressure and temperature in the shock vein attained 23 GPa and 2000°C. This new mineral and the mineral name (tuite) have been approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association.