On the labyrinthine crystal chemistry of meyerhofferite, Ca2B6O6(OH)10•2H2O

Natural borates represent the most important source of boron: in 2017, the world production accounted for about 9.8 millions of tons. Natural borates are also being used for the production of radiation-shielding concretes, because of the elevated ability of 10B to absorb thermal neutrons. However, the most used natural borates (i.e., borax) have proved to induce a drastic effect on setting and hardening, coupled with a lowering of durability of concretes (due to the high Na-content). We are investigating the chemical stability and high-T/high-P crystal-chemistry of meyerhofferite (Ca2B6O6(OH)10•2H2O), which contains 46.7 wt% B2O3 and 28 wt% H2O, with a multi-methodological approach: a SC neutron diffraction experiment is necessary to obtain a full structural model of meyerhofferite, with an unambiguous location of all the H sites and the description of the complex H-bonding network