Raman spectroscopy of newberyite, hannayite and struvite

The phosphate minerals hannayite, newberyite and struvite have been studied by Raman spectroscopy using a thermal stage. Hannayite and newberyite are characterised by an intense band at around 980 cm−1 assigned to the v1 symmetric stretching vibration of the HPO4 units. In contrast the symmetric stretching mode is observed at 942 cm−1 for struvite. The Raman spectra are characterised by multiple v3 anti-symmetric stretching bands and v2 and v4 bending modes indicating strong distortion of the HPO4 and PO4 units. Hannayite and newberyite are defined by bands at 3382 and 3350 cm−1 attributed to HOPO3 vibrations and hannayite and struvite by bands at 2990, 2973 and 2874 assigned to NH4+ bands. Raman spectroscopy has proven most useful for the analysis of these 'cave' minerals where complex paragenetic relationships exist between the minerals.