R4: Mineral sciences of the Earth surface

[R4-07] Neutron diffraction and Raman spectroscopy of nesquehonite:Which is the correct chemical formula, MgCO_3^・3H₂O or Mg(OH)(HCO₃)・2H₂O?

「発表賞エントリー」

*Gen-ichiro YAMAMOTO¹, Atsushi KYONO¹, Jun ABE², Asami SANO -FURUKAWA³, Takanori HATTORI³ (1. Univ. Tsukuba, 2. CROSS, 3. JAEA)

Keywords:Nesquehonite, Neutron diffraction, Raman spectroscopy, Hydrogen bonding network

Neutron diffraction and Raman spectroscopy were performed to determine the structure and chemical formula of nesquehonite. The difference between our study and Hales et al. (2008) strongly indicates that nesquehonite can have two chemical formulas, Mg(OH)(HCO₃)・2H₂O and MgCO₃・3H₂O depending on the pH in the solution. That is, nesquehonite grown in a solution with pH around neutrality would have the chemical formula of Mg(OH)(HCO₃)・2H₂O, but that in a strongly alkaline solution results in the chemical formula of MgCO₃・3H₂O.