Ferrierit-Mg a Ba bohatý heulandit z Chvaletic u Přelouče (Česká republika)

Two zeolites are described from the pyrite-manganese deposit Chvaletice near Přelouč, central Bohemia, Czech Republic. Ferrierite-Mg forms brown, up to 5 mm long flat needles, radially arranged, which grow on grey-brown fine-grained rock composed of quartz, pyrite and Mn-silicates. The unit-cell parameters of ferrierite-Mg, refined from the powder X-ray diffraction data, are a = 19.162(14), b = 14.125(13), c = 7.495(6) Å and V = 2028.8(9) Å3 (space group Immm). Chemical analyses correspond to the empirical formula (Mg2.66Ca0.44Mn0.41Fe0.30Ba0.29K0.16Na0.10Sr0.03)Σ4.39(Al7.77 Si27.96O72)·18 H2O. The Ba-rich heulandite forms aggregates up to several cm in size composed of transparent gold-brown grains with characteristic pearly luster at cleavage planes. The unit-cell parameters of heulandite, refined from the powder X-ray diffraction data, are a = 17.732(2), b = 17.823(4), c = 7.4290(15) Å, β = 116.3(2) ° and V = 2104.2(6) Å3 (space group Cm). In BSE images, its aggregates are not homogenous. Ba-poor part of analyses corresponds to heulandite-Ca and heulandite-K, Ba-rich part beside Ca- and K-dominant members also to very rare heulandite-Ba. Both studied zeolites contain a significant content of Mn, ranging between 0.32 - 0.70 apfu (ferrierite-Mg) and 0.09 - 0.28 apfu (Ba-rich heulandite).