Virgilite is hexagonal, P6222 or P6422; a = 5.132, c = 5.454A; n = 1.520, uniaxial (−). Cell content of the crystals studied is Li0.61 (Si2.37Al0.60Fe0.02P0.01)O6. Virgilite is found in volcanic glass of unusual composition from Macusani, Peru. It is the only naturally-occurring representative of the solid-solution series between β-quartz (Qz) and LiAlSi2O6 (Sp) with a stuffed β-quartz structure. The composition of our material corresponds to Sp61Qz39.

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