Synthesis and Raman spectroscopic characterisation of the oxalate mineral wheatleyite Na₂Cu²⁺(C₂O₄)₂·2H₂O

The mineral wheatleyite has been synthesised and characterised by Raman spectroscopy complimented with infrared spectroscopy. Two Raman bands at 1434 and 1470 cm −1 are assigned to the ν (CO) stretching mode and implies two independent oxalate anions. Two intense Raman bands observed at 904 and 860 cm −1 are assigned to the ν(CC) stretching mode and support the concept of two non‐equivalent oxalate units in the wheatleyite structure. Two strong bands observed at 565 and 585 cm −1 are assigned to the symmetric CCO in plane bending modes. The Raman band at 387 cm −1 is attributed to the CuO stretching vibration and the bands at 127 and 173 cm −1 to OCuO bending vibrations. A comparison is made with Raman spectra of selected natural oxalate bearing minerals. Oxalates are markers or indicators of environmental events. Oxalates are readily determined by Raman spectroscopy. Thus, deterioration of works of art, biogeochemical cycles, plant metal complexation, the presence of pigments and minerals formed in caves can be analysed.