underthescopemineral: Chiavennite, Analcime CaMn2+(BeOH)2Si5O13·2H2O, Na(AlSi2O6)·H2O
underthescopemineral: Chiavennite, Analcime CaMn2+(BeOH)2Si5O13·2H2O, Na(AlSi2O6)·H2O Locality:Tvedalen, Larvik, Vestfold, Norway Field of View: 2.46 mm Aggregates of orange chiavennite crystals Collection and photo OT. LjøstadChiavennite is closely related to Ferrochiavennite, which is its Fe analog. See also the related tvedalite and another chemically close mineral, harstigite. Re-investigations of Chiavennite from the TL indicate that at room temperature chiavennite is monoclinic with spacegroup P21/c; the mineral becomes orthorhombic (Pbcn) upon dehydration due to destruction of water(extraframework)-oxygen(cavity walls) hydrogen bonds. Occurs as coating beryl in late-stage pegmatites (Tanno, Italy); in vugs in syenite pegmatites (Norway). -- source link