Micro-Raman Characterization of the Lapeyreite Mineral, the Alpes-Maritimes Region, Nice, France

Abstract

The Raman spectroscopy is performed for the first time on the new discovered secondary copper arsenate mineral, lapeyreite [Cu₃O[AsO₃(OH)]₂.0.75H₂O]. The bands attributed to two main vibrating (CuO₅ and AsO₄) units are readily identified in the Raman spectrum. Symmetric stretching modes at 1047 cm^-1 and at 627 and 405 cm^-1 are assigned to (n₁)CuO₅, (n₂)AsO₄ and (n₃)AsO₄ units, respectively. Bending vibration modes in the Raman spectrum are assigned to (n₂)AsO₄ units at 214, 198 and 188 cm^-1 and to (n₂)CuO₅ units at 141 and 100 cm^-1. In addition, As-O bond and O-H-O bond lengths in the structure of lapeyreite were assigned from the FT-IR at 3420, 2870 and 1640 cm^-1. The position and the intensity of both Raman vibrations reveal that the secondary occurring lapeyreite mineral is hydrothermally altered from the primary occurring cuprite mineral.