Hezuolinite, (Sr,REE)(4)Zr(Ti,Fe3+,Fe2+)(2)Ti2O8(Si2O7)(2), a new mineral species of the chevkinite group from Saima alkaline complex, Liaoning Province, NE China

作者：Yang, Zhuming; Giester, Gerald^*; Ding, Kuishou; Tillmanns, Ekkehart

来源：European Journal of Mineralogy, 2012, 24(1): 189-196.

DOI：10.1127/0935-1221/2011/0023-2158

• hezuolinite
• new mineral
• chemical composition
• rare earths
• crystal structure
• chevkinite group
• Saima alkaline complex
• China

Hezuolinite is a new mineral species occurring as an accessory mineral in the Saima alkaline complex in Liaoning Province, NE China. The mineral occurs in a green-aegirine nepheline syenite as non-metamict grains and is associated with microcline, nepheline, aegirine, biotite, eudialyte, rinkite and titanite. The anhedral crystals are several hundred micrometres in size. The mineral is black with dark-brown streak. It is translucent with a resinous luster. Cleavage or parting was not observed. It is brittle with a conchoidal fracture. The hardness is VHN100 683-964 kg mm(-2) (5.5-6 on Mohs' scale). The measured density is 4.28 g cm(-3), and the calculated value is 4.30 g cm(-3) from the empirical chemical formula. Optically, hezuolinite is biaxial negative, with n > 1.8 and 2V = 75 degrees. The dispersion is strong with r > v. The mineral shows a strong pleochroism, from pale brown to dark brown. The average of twenty-five analyses leads to the empirical formula (Sr2.15Ce0.55 La-0.49 Ca0.49Na0.12Nd0.09 Pr0.03Th0.03Sm0.01 Eu-0.01)(Sigma 3.98) (Zr-0.82 Fe2+ 0.14Hf0.02Mn0.01)(Sigma 1.00) (Ti-1.38 Fe3+ (0.36) Fe2+ (0.14) Al-0.04 Nb-0.02)(Sigma 1.94)Ti2O8 (Si2.01O7)(2), on the basis of O = 22. The simplified formula is (Sr,REE)(4)Zr(Ti,Fe3+, Fe2+)(2)Ti2O8(Si2O7)(2), ideally Sr2REE2Zr(Fe2+)Ti3O8(Si2O7)(2).
The five strongest reflections in the X-ray powder-diffraction pattern [d in angstrom (I)(hkl)] are: 2.98(100)(-204), 3.02(90)(-313), 1.96(90)(024), 2.18(40)(-422), and 2.84(70)(020). The structure was solved and refined in space group C2/m, with a = 13.973(3), b = 5.6984(11), c = 11.988(2) angstrom, beta = 114.10(1)degrees, V = 871.3(3) angstrom(3) 3, Z = 2, to R1 = 0.037, wR2 = 0.097.
The structure of hezuolinite is similar to rengeite. The changes of Sr-O, Zr-O and Ti(1)-O distances confirm partial substitutions of REE for Sr, and Fe for Ti. The sites of O(1), O(2) and O(3) of the hezuolinite structure (C2/m) are split into O(1) and O(1'), O(2) and O(2'), O(3) and O(3') sites in the rengeite structure (P2(1)/a), respectively. The Si(1)-O(7)-Si(2) angle in hezuolinite is 175.8 degrees, and is significantly less bent than in rengeite (169.7 degrees). The observed systematic extinctions are in agreement with space group C2/m. Hezuolinite is a member of the perrierite-subgroup and can be considered as a chemical intermediate between rengeite and perrierite.

• 出版日期2012-2
• 单位中国科学院地质与地球物理研究所兰州油气资源研究中心; 中国科学院地质与地球物理研究所