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Journal Article 
A vibrational spectroscopic study of the silicate mineral ardennite-(As) 
Frost, RL; López, A; Xi, Y; Scholz, R; Gandini, AL 
In Press 
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
ISSN: 1386-1425
EISSN: 1873-3557 
We have used a combination of scanning electron microscopy with EDX and vibrational spectroscopy to study the mineral ardennite-(As). The mineral ardennite-(As) of accepted formula Mn4(2+)(Al,Mg)6(Si3O10)(SiO4)2(AsO4,VO4)(OH)6 is a silicate mineral which may contain arsenate and/or vanadates anions. Because of the oxyanions present, the mineral lends itself to analysis by Raman and infrared spectroscopy. Qualitative chemical analysis shows a homogeneous phase, composed by Si, Mn, Al and As. Ca and V were also observed in partial substitution for Mn and As. Raman bands at 1197, 1225, 1287 and 1394cm(-1) are assigned to SiO stretching vibrations. The strong Raman bands at 779 and 877cm(-1) are assigned to the AsO4(3-) antisymmetric and symmetric stretching vibrations. The Raman band at 352cm(-1) is assigned to the ν2 symmetric bending vibration. The series of Raman bands between 414 and 471cm(-1)are assigned to the ν4 out of plane bending modes of the AsO4(3-) units. Intense Raman bands observed at 301 and 314cm(-1) are attributed to the MnO stretching and bending vibrations. Raman bands at 3041, 3149, 3211 and 3298cm(-1) are attributed to the stretching vibrations of OH units. There is vibrational spectroscopic evidence for the presence of water adsorbed on the ardennite-(As) surfaces. 
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