Dehydration processes in borate minerals: pentahydroborite and nifontovite from Fuka Mine, Okayama Prefecture, Japan

Abstract

Data on the dehydration of pentahydroborite, CaB2O(OH)6·2H2O and nifontovite, Ca3B6O6(OH)12·2H2O from the Fuka mine, Japan are presented. Critical temperatures of the dehydration of the borates were determined by thermogravimetric analysis/differential thermal analysis measurements. The untreated mineral samples and their heating products were investigated by X-ray diffraction and Raman spectroscopy. Upon dehydration, both minerals decompose and undergo amorphization, and at greater temperatures crystallize as an orthorhombic calcium borate, CaB2O4 (Pnca). The dehydration paths of the two minerals are different, with nifontovite showing a greater resistance to decomposition and amorphization than pentahydroborite. Differences in the dehydration processes are related to the residuals of the water content and structural accommodation of the borate polyanion.

Infrared and Raman spectroscopic characterization of the borate mineral colemanite – CaB3O4(OH)3·H2O – implications for the molecular structure

“…Raman spectroscopy has proven most useful for the study of secondary minerals [26,[32][33][34][35][36][37]. To the best of the authors' knowledge, there have been very few vibrational spectroscopic studies of borate minerals [38][39][40][41][42]. A Raman and infrared spectrum of colemanite may be found on the RRUFF data base at http://rruff.info/ colemanite/display=default/R050102, however, no interpretation is given.…”

Boron in Prebiological Evolution

“…Colemanite and ulexite have been used as borate sources (both minerals contain calcium) in previous experiments, to mimic prebiological reactions [44] . The number of calcium borate minerals is vast and, typically, they contain a very limited number of ions [100–112] . New calcium borate compounds have been obtained under synthetic conditions, relatable to prebiotic environments [113–115] .…”