Hezuolinite, (Sr,REE) (sub 4) Zr(Ti,Fe (super 3+) ,Fe (super 2+) ) (sub 2) Ti (sub 2) O (sub 8) (Si (sub 2) O (sub 7) ) (sub 2) , a new mineral species of the chevkinite group from Saima alkaline complex, Liaoning Province, NE 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 VHN (sub 100) 683-964 kg mm (super -2) (5.5-6 on Mohs' scale). The measured density is 4.28 g cm (super -3) , and the calculated value is 4.30 g cm (super -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 (Sr (sub 2.15) Ce (sub 0.55) La (sub 0.49) Ca (sub 0.49) Na (sub 0.12) Nd (sub 0.09) Pr (sub 0.03) Th (sub 0.03) Sm (sub 0.01) Eu (sub 0.01) ) (sub Sigma 3.98) (Zr (sub 0.82) Fe (super 2+) (sub 0.14) Hf (sub 0.02) Mn (sub 0.01) ) (sub Sigma 1.00) (Ti (sub 1.38) Fe (super 3+) (sub 0.36) Fe (super 2+) (sub 0.14) Al (sub 0.04) Nb (sub 0.02) ) (sub Sigma 1.94) Ti (sub 2) O (sub 8) (Si (sub 2.01) O (sub 7) ) (sub 2) , on the basis of O=22. The simplified formula is (Sr,REE) (sub 4) Zr(Ti,Fe (super 3+) ,Fe (super 2+) ) (sub 2) Ti (sub 2) O (sub 8) (Si (sub 2) O (sub 7) ) (sub 2) , ideally Sr (sub 2) REE (sub 2) Zr(Fe (super 2+) )Ti (sub 3) O (sub 8) (Si (sub 2) O (sub 7) ) (sub 2) . The five strongest reflections in the X-ray powder-diffraction pattern [d in Aa (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) Aa, beta =114.10(1) degrees , V=871.3(3) Aa (super 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 (sub 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.