Abstract
The results of perennial research of several Serbian zeolitic tuffs enriched with HEU-type minerals are presented in this paper. There are several recognized zeolitic tuff deposits containing HEU-type minerals: Zlatokop, Igros, Beocin, Toponica, Slanci, but their comparative mineralogical and crystallochemical features have not been studied in detail so far. These zeolitic tuff deposits are spatially and genetically connected to volcanic and pyroclastic rocks of marine and lake environments of Senonian and Eocene, and Neogene age, respectively. As a result of devitrification and diagenesis process of volcanic glass within zeolitic tuffs hypocrystalline porphiry and vitroclastic textures occur. The studied zeolitic tuffs are mainly composed of heulandite occuring in a form of needle- to plate-like crystals of 0,1 do 100 ?m in length, associated with other silicates. Depending on the type and content of exchangeable cations as well as the thermal stability of these raw materials, 24 clinoptilolite-Ca and heulandite-Ca can be distinguished. The values of cation exchange capacity and surface area capacity range from 96 to 166 meq/100 g, and from 8,0 to 10,5 meq/100 g, respectively. HEU-type minerals can be distinguished either by a Si/Al ratio or arrangement of extra framework cations within the crystal structure of these minerals.
Highlights
HEU-type minerals are presented in this paper
recognized zeolitic tuff deposits containing HEU-type minerals
crystallochemical features have not been studied in detail
Summary
Zbog svojih fizičko–hemijskih svojstava, jedna od ekonomski najznačajnijih grupa mineralnih sirovina. Godine u svetu je eksploatisano oko 3 miliona tona prirodnih zeolitskih tufova (uglavnom klinoptilolitskog i šabazitskog sastava). Zeolitski tufovi predstavljaju mineralna ležišta prirodnih zeolita, od kojih najveći ekonomski interes imaju tufovi klinoptilolit-hojlanditskog sastava. Na osnovu preporuke Međunarodne mineraloške asocijacije (International Mineralogical Association − IMA) − za nove minerale i imena minerala, podkomiteta za zeolite, minerali hojlandit i klinoptilolit (HEU-tip) definisani su kao zeolitski minerali gde je atomski odnos Si/Al < 4, odnosno Si/Al > 4 [10]. Zadovoljavajuća kristalohemijska i mineraloška svojstva zeolitskih tufova daju mogućnost njihove primene u različitim procesima adsorpcije, jonske izmene ili katalitičkim reakcijama. Rovni uzorci zeolitskih tufova obeleženi Beočin (B), Slanci (S), Igroš (I), Zlatokop (Z), Toponica (T) pripremljeni su za mineraloška, kristalohemijska i druga ispitivanja (mleveni uzorci su mokro prosejani, 100% < 63 μm). Uzorci su analizirani u temperaturnom opsegu od 25 od 1000 °C sa korakom od 5 °C/min u atmosferi vazduha
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