Lavinskyite-1M from Cerchiara mine, Liguria, Italy: the monoclinic MDO equivalent of lavinskyite-2O

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Marco E. Ciriotti
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Lavinskyite-1M from Cerchiara mine, Liguria, Italy: the monoclinic MDO equivalent of lavinskyite-2O

Messaggio da Marco E. Ciriotti » lun 26 feb, 2018 11:54

Prossima pubblicazione.

Referenza:
▪ Kolitsch, U., Merlino, S., Belmonte, D., Carbone, C., Cabella, R., Lucchetti, G., Ciriotti, M.E. (2018): Lavinskyite-1M, K(LiCu)Cu6(Si4O11)2(OH)4, the monoclinic MDO equivalent of lavinskyite-2O (formerly lavinskyite), from the Cerchiara manganese mine, Liguria, Italy. European Journal of Mineralogy, 30, (in press).
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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TOSATO FABIO
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Re: Lavinskyite-1M from Cerchiara mine, Liguria, Italy: the monoclinic MDO equivalent of lavinskyite-2O

Messaggio da TOSATO FABIO » lun 26 feb, 2018 19:33

Complimenti agli autori e allo scopritore!
Tosato Fabio
"Il vero viaggio di scoperta non consiste nel cercare nuove terre, ma nell'avere nuovi occhi." M. Proust
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Marco E. Ciriotti
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Re: Lavinskyite-1M from Cerchiara mine, Liguria, Italy: the monoclinic MDO equivalent of lavinskyite-2O

Messaggio da Marco E. Ciriotti » gio 01 mar, 2018 10:23

Prossima pubblicazione.

Referenza:
▪ Kolitsch, U., Merlino, S., Belmonte, D., Carbone, C., Cabella, R., Lucchetti, G., Ciriotti, M.E. (2018): Lavinskyite-1M, K(LiCu)Cu6(Si4O11)2(OH)4, the monoclinic MDO equivalent of lavinskyite-2O (formerly lavinskyite), from the Cerchiara manganese mine, Liguria, Italy. European Journal of Mineralogy, 30, (in press).

Abstract:
Lavinskyite-1M, a monoclinic MDO (Maximum Degree of Order) polytype related to the orthorhombic MDO polytype lavinskyite-2O (formerly lavinskyite, now redefined), was identified in samples fromthe Cerchiaramanganesemine (Liguria, Italy). Both polytypes have the same ideal chemical formula, K(LiCu)Cu6(Si4O11)2(OH)4. Lavinskyite-1M was originally approved as “liguriaite”, but was subsequently redefined as lavinskyite-1M (IMA proposal 16-E).
Lavinskyite-1M occurs as blue, micaceous aggregates embedded in calcite-filled microfractures and veinlets, where it is associated with calcite, quartz, norrishite and “schefferite” (a Mn-bearing variety of diopside). Lavinskyite-1M is translucent to transparent, bluish to pale blue in colour with a very pale blue to whitish streak and vitreous lustre; it is non-fluorescent. Individual, always indistinct platelets are up to ∼0.15 mm in length. The crystals are tabular (100) and elongate along [001]. Lavinskyite-1M is brittle with perfect cleavage parallel to {100}, and uneven fracture. The estimated Mohs hardness is ∼5. The calculated density is 3.613 g/cm3 (for empirical formula). Optically, it is biaxial positive, with α = 1.674(2); β = 1.692(3) and γ = 1.730(3); 2Vγ is very large, ∼75° (est.), 2Vγ (calc.) = 70°. Pleochroism is moderate: X (pale) blue, Y pale blue and Z pale blue with faint greenish tint; absorption X≥Z≥Y. Orientation: X∧ a∼20° (probably in obtuse beta), Y = b, Z∼c; optical elongation is positive and the optical axis plane is parallel to (010). No dispersion was observed.
Chemical analysis (quantitative SEM-EDS and LA-ICP-MS) of two samples yielded the empirical formulae (based on 26 O atoms) (K1.08)Σ1.08(Li0.89Mg0.36Cu0.33Na0.22Mn2+0.04)Σ1.86Cu6.00Si8.08O22(OH)4 and (K1.08)Σ1.08(Li0.89Cu0.35Mg0.28Na0.22Mn2+0.04)Σ1.78Cu6.00Si8.12O22(OH)4. Strongest lines in the X-ray powder diffraction pattern are [d in Å (Icalc) hkl]): 10.216 (100) 100, 9.007 (20) 110, 4.934 (19) 210, 3.983 (19) 230, 3.353 (33) 310, 2.8693 (22) 241, 2.6155 (35) 161, 2.3719 (23) 20-2. The crystal structure has been solved, using single-crystal X-ray diffractometer data (Rint = 4.60%), by direct methods and refined in space group P21/c (no. 14) to R1 = 5.10% and wR2all = 13.92% [1786 ‘observed’ reflections with Fo>4s(Fo), 199 parameters]. Refined unit-cell parameters are: a = 10.224(2), b = 19.085 (4), c = 5.252(1)Å, β = 92.23(3)°, V = 1024.0(4)^Å3 (Z = 2). The chemical composition and crystal structure are supported by micro-Raman spectra.
Lavinskyite-1M has a sheet structure consisting of corrugated brucite-like (CuO2)n layers with amphibole-type (SiO3)n chains joined to both their upper and lower surfaces. Adjacent complex sheets are linked by [5]-coordinated Li atoms and Cu atoms in square coordination (nearly planar) and interlayer K atoms. Lavinskyite-1M is isostructural with a hypothetical monoclinic MDO polytype of plancheite, not yet found in nature, while lavinskyite-2O is isostructural with plancheite. It appears that a complex and delicate interplay between the Li:Cu and Cu:Mg ratios (lower in lavinskyite-1M), along with an additional influence of impurity cations such as Na and different conditions of formation, results in a stabilisation of the 1M polytype. The origin of lavinskyite-1M can be related to a complex, multi-stage hydrothermal evolution of the primary Fe-Mn ore at Cerchiara, which experienced a diffuse alkali metasomatism under strongly oxidising conditions and produced mineral assemblages enriched in Na, K and Li, while providing also appreciable amounts of Ba, Sr, Ca and Cu.
Marco E. Ciriotti

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Re: Lavinskyite-1M from Cerchiara mine, Liguria, Italy: the monoclinic MDO equivalent of lavinskyite-2O

Messaggio da TOSATO FABIO » gio 01 mar, 2018 11:38

Complimenti a tutti.
Tosato Fabio
"Il vero viaggio di scoperta non consiste nel cercare nuove terre, ma nell'avere nuovi occhi." M. Proust
Noi siamo anche quello che non siamo riusciti ad essere.
Sic transit gloria mundi.

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