- journal_title：Mineralogical Magazine
- Contributor：S. J. Mills ; A. G. Christy ; A. R. Kampf ; R. M. Housley ; G. Favreau ; J.-C. Boulliard ; V. Bourgoin
- Publisher：Mineralogical Society of Great Britain and Ireland
- Date：2012-10-01
- Format：text/html
- Language：en
- Identifier：10.1180/minmag.2012.076.5.01
- journal_abbrev：Mineralogical Magazine
- issn：0026-461X
- volume：76
- issue：5
- firstpage：1337
- section：CNMNC Newsletter 14
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 (
Al0.04)Σ2.00Al1.01 (
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 R3İ, with a = 5.340(2), c = 88.01(2) Å, V = 2173.70(15) Å3 and Z = 9. The crystal structure was refined to R1 = 0.0931 for 370 unique reflections [Fo > 4σ(F)] and R1 = 0.0944 for all 381 unique reflections. It has the longest periodic layer stacking sequence for a layered double hydroxide compound reported to date.