A series of manganoan fluorophlogopites K(Mg, Mn)₃Si₃AlO₁₀F₂ and the corresponding germanate micas K(Mg, Mn)₃Ge₃AlO₁₀F₂ with various Mg/Mn ratios were synthesized from melts of mixtures of KF, MgF₂, MnF₂, MgO, MnO, Al₂O₃ and SiO₂ or GeO₂ in appropriate ratios. Products were examined mainly by the X-ray diffraction technique, and variations of structural parameters of the manganoan micas were estimated from unit cell parameters. In K(Mg, Mn)₃Si₃AlO₁₀F₂, the substitution of Mg²⁺ ions by Mn²⁺ decreases the tetrahedral rotation angle α, and the tetrahedral sheet is expected to have a nearly hexagonal form at the solubility limit. In K(Mg, Mn)₃Ge₃AlO₁₀F₂, the solubility range is more extended than that in the corresponding silicate micas as is expected form the large [Ge₃AlO₁₀] tetrahedral sheet. However, the Mn-rich end member KMn₃Ge₃AlO₁₀F₂ could not be synthesized, and the crystal still has a large α value at the solubility limit. It was shown that the substitution of larger cations at the octahedral sites decreases rapidly the thermal stability of K(Mg, Mn)₃Ge₃AlO₁₀F₂.

View full abstract

Kinichilite, a new mineral from the Kawazu mine, is hexagonal with a=9.419 Å, c=7.666 Å, space group P6₃ or P6₃⁄m. The empirical formula derived from the chemical analysis is: (Fe²⁺_1.13Mg_0.47Zn_0.43Mn²⁺_0.17)_Σ2.20(Te_2.97Se_0.03)_Σ3.00 O_9.00(H_1.38Na_0.22)_Σ1.60·3.2H₂O, corresponding to Fe²⁺ dominant analogue of zemannite.
It is dark brown in colour. Subadamantine luster and brown streak. No cleavage. Density (calc.) 3.96 g/cm³ from normalized empirical formula and Z=2.

View full abstract

Although structurally ZrS₂ is very similar to polytypic SnS₂, PbI₂, CdI₂ and others, no evidence for structural polytypism was observed in 50 crystals studied by the Weissenberg X-ray method. All crystals were shown to be type 2H, [(A_γB)]_n. Also no crystals showed structural disorder, a property common for polytypic compounds.

View full abstract