Zincalstibite-9R: the first nine-layer polytype with the layered double hydroxide structure-type

S. J. Mills, A. G. Christy, A. R. Kampf, R. M. Housley, G. Favreau, J.-C. Boulliard, V. Bourgoin
2012 Mineralogical magazine  
Zincalstibite-9R, a new polytype in the hydrotalcite supergroup is reported from the Monte Avanza mine, Italy. It occurs as pale blue curved disc-like tablets flattened on {001} intergrown to form rosettes typically less than 50 μm in diameter, with cyanophyllite and linarite in cavities in baryte. Zincalstibite-9R is uniaxial (–), with refractive indices ω = 1.647(2) and ε = 1.626(2) measured in white light. The empirical formula (based on 12 OH groups) is (Zn1.09 2+Cu0.87
more » ... +Al0.04)Σ2.00Al1.01(Sb0.97 5+Si0.02)Σ0.99(OH)12, and the ideal formula is (Zn,Cu)2Al(OH)6[Sb(OH)6]. Zincalstibite-9R crystallizes in space group R , with a = 5.340(2), c = 88.01(2) Å, V = 2173.70(15) Å3 and Z = 9. The crystal structure was refined to R 1 = 0.0931 for 370 unique reflections [F o > 4σ(F)] and R 1 = 0.0944 for all 381 unique reflections. It has the longest periodic layer stacking sequence for a layered double hydroxide compound reported to date.
doi:10.1180/minmag.2012.076.5.01 fatcat:lnafvg27yre5lmfyi76rpktjoi