Raman spectroscopic study of the tellurite minerals: Carlfriesite and spiroffite

Raman spectroscopy has been used to study the tellurite minerals spiroffite and carlfriesite, which are minerals of formula type A2(X3O8) where A is Ca2+ for the mineral carlfriesite and is Zn2+ and Mn2+ for the mineral spiroffite. Raman bands for spiroffite observed at 721 and 743 cm−1, and 650 cm−1 are attributed to the ν1 (Te3O8)2− symmetric stretching mode and the ν3 (Te3O8)2− antisymmetric stretching modes, respectively. A second spiroffite mineral sample provided a Raman spectrum with bands at 727 cm−1 assigned to the ν1 (Te3O8)2− symmetric stretching modes and the band at 640 cm−1 accounted for by the ν3 (Te3O8)2− antisymmetric stretching mode. The Raman spectrum of carlfriesite showed an intense band at 721 cm−1. Raman bands for spiroffite, observed at (346, 394) and 466 cm−1 are assigned to the (Te3O8)2−ν2 (A1) bending mode and ν4 (E) bending modes. The Raman spectroscopy of the minerals carlfriesite and spiroffite are difficult because of the presence of impurities and other diagenetically related tellurite minerals.