Dachiardite-K (К2Са)(Аl4Si20O48)・13Н2O, a new zeolite from the Eastern Rhodopes, Bulgaria
Chukanov N. V., EnchevaS., Petrov P., Pekov I. V., Belakovskiy D. I., Britvin S. N., Aksenov S. M.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2016. V. 145. N 1. P. 68-79
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Language: Russian
Abstract
The new zeolite—dachiardite-K (IMA No. 2015-041)—the K-dominant member of the dachiardite series with the idealized formula (К2Са)(Аl4Si20O48)・13Н2O, has been found in salbands of opal-chalcedony hydrothermal veinlets cross-cutting hydrothermally altered effusive rocks of the Zvezdel paleovolcanic complex near the village of Austa, Momchilgrad Municipality, Eastern Rhodopes, Bulgaria. It occurs there in association with chalcedony, opal, dachiardite-Ca, dachiardite-Na, ferrierite-Mg, ferrierite-K, clinoptilolite-Ca, clinoptilolite-K, mordenite, smectite, celadonite, calcite, and barite. Dachiardite-K forms spherical radial aggregates, up to 8 mm in diameter, consisting of split needle-shaped individuals. Color is white to colorless. Perfect cleavage is observed on (100). Dmeas = 2.18(2), Dcalc = 2.169 g/cm3. The IR spectrum is given. Dachiardite-K is biaxial (+), α = 1.477 (calc.), β = 1.478(2), γ = 1.481(2), 2Vmeas = 65(10)°. The chemical composition (electron microprobe, mean of 6 spot analyses, H2O determined by thermogravimetric method, wt %) is: K2O 4.51, CaO 3.27, BaO 0.41, A12O3 10.36, SiO2 67.90, H2O 13.2, total 99.65. The empirical formula is: H26.23K1.71Ca1.04Ba0.05Al3.64Si20.24O61. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 9.76 (24) (001), 8.85 (58) (200), 4.870 (59) (002), 3.807 (16) (202), 3.768 (20) (112, 020), 3.457 (100) (220), 2.966 (17) (602). Dachiardite-K is monoclinic, space group C2/m, Cm or C2; unit-cell parameters refined from powder data are: a = 18.670(8), b = 7.511(3), c = 10.231(4) Å, β = 107.79(3)°, V= 1366(1) Å3, Z = 1. The type specimen is deposited in the Earth and Man National Museum, Sofia, Bulgaria, with the registration number 23927.
Key words: dachiardite-K, zeolite, new mineral species, Zvezdel paleovolcanic complex, Eastern Rhodopes, Bulgaria.
