NEW DATA FOR CHIAVENNITE AND FERROCHIAVENNITE

作者：Grice Joel D^*; Friis Henrik; Kristiansen Roy

来源：The Canadian Mineralogist, 2016, 54(1): 21-32.

DOI：10.3749/canmin.1500068

• fenochiavennite
• chiavennite
• interrupted zeolite framework
• beryllium silicate
• ciystal structure
• syenitic pegmatite
• granite pegmatite
• Italy
• Norway
• Sweden
• Madagascar

Chiavennite (Mn endmember) and ferrochiavennite (Fe endmember) are beryllium silicate zeolites with chemical compositions close to Ca1-2(Mn,Fe)Si5Be2O13(OH)(2)2H(2)O. Five chiavennite crystals from four different localities, Chiavenna, Italy; Telemark, Norway; Uto, Sweden; and Ambatovita, Madagascar, were chosen for crystal-structure analysis. Initially all had been reported to be orthorhombic, but all are monoclinic, with a beta angle near 90, as is ferrochiavennite from Blafjell, Norway. Twinning on {100} is common. Chiavennite and ferrochiavennite are isostructural. The zeolite structure consists of intersecting channels of nine-, six-, five-, and four-fold rings. All five structures have one Ca site in common while chiavennite from Uto and ferrochiavennite from Blafjell have a second, partially filled, Ca site. Hydrogen atoms were located in all five structures. Hydrogen bonding is similar but not identical in all five structures. The H atoms associated with BeO4 tetrahedra act as terminations to a polymerization sequence causing chiavennite and ferrochiavennite to be interrupted zeolite structures.

• 出版日期2016-1-1