Université de Fribourg

Melilite-group minerals at Oldoinyo Lengai, Tanzania

Wiedenmann, Daniel ; Keller, Jörg ; Zaitsev, Anatoly N.

In: Lithos, 2010, p. -

Oldoinyo Lengai and the volcanic centres of the Lake Natron–Engaruka province contain melilite as a widespread mineral. Extraordinarily Na–Al-rich melilites (up to 6 wt.% Na₂O and 9 wt.% Al₂O₃) from recent explosive eruptions are among the most Na-rich ever reported. Their unusual mineral composition leads to optical properties with vivid birefringence colours of 2nd order. The...

Université de Fribourg

Alumoåkermanite, (Ca,Na)₂(Al,Mg,Fe²⁺)(Si₂O₇), a new mineral from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, northern Tanzania

Wiedenmann, Daniel ; Zaitsev, A. N. ; Britvin, S. N. ; Krivovichev, S. V. ; Keller, J.

In: Mineralogical Magazine, 2009, vol. 73, no. 3, p. 373-384

Alumoåkermanite, (CaNa)₂(Al,Mg,Fe²⁺)(Si₂O₇), is a new mineral member of the melilite group from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, Tanzania. The mineral occurs as tabular phenocrysts and microphenocrysts in melilite-nephelinitic ashes and lapilli-tuffs. Alumoåkermanite is light brown in colour; it is transparent, with a vitreous lustre and the streak...