Original paper

Chabazite-offretite epitaxial overgrowths in cornubianite from Passo Forcel Rosso, Adamello, Italy

Passaglia, Elio; Tagliavini, Alessandra

European Journal of Mineralogy Volume 6 Number 3 (1994), p. 397 - 406

35 references

published: Jun 7, 1994
manuscript accepted: Jan 21, 1994
manuscript received: Jul 5, 1993

DOI: 10.1127/ejm/6/3/0397

BibTeX file

ArtNo. ESP147050603006, Price: 29.00 €

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Abstract The first occurrence of the zeolite offretite in Italy is described in a cornubianite rock from Passo Forcel Rosso, Adamello. The mineral occurs as milky-white fibrous overgrowths in structural epitaxy on the (0001) crystal faces of hyaline platy chabazite ("herschelite habit"), associated with large chabazite rhombohedra and yellowish spherules of saponite. Crystal chemical characterization of the zeolitic phases indicates anomalously high Mg contents in the offretite as well as the chabazite overgrowths. The chemistry of the offretites is reviewed, showing that the Si/Al ratio and K content are relatively constant, whereas the Ca/Mg ratio varies considerably, there being very few Mg-rich samples. The paragenesis of the newly-formed minerals is interpreted in the light of the host-rock chemistry.


zeolitesoffretiteMg-rich chabaziteepitaxycrystal chemistry