Title
Bosoite, a new silica clathrate mineral from Chiba Prefecture, Japan
Author
Koichi Momma, Takuji Ikeda , Toshiro Nagase , Takahiro Kuribayashi , Chibune Honma , Katsumi Nishikubo , Naoki Takahashi , Masayuki Takada , Yoshitaka Matsushita , Ritsuro Miyawaki and Satoshi Matsubara
Year
2020
Journal
Mineralogical Magazine
Abstract
Bosoite (IMA2014-023) is a new silica clathrate mineral containing hydrocarbon
molecules in its crystal structure. Bosoite can be structurally considered as a silica
analogue of the structure-H gas hydrate, where guest molecules are trapped in cage-like
voids constructed of the host framework. The mineral occurs in the Miocene tuffaceous
sedimentary rocks at Arakawa, Minami-boso City, Chiba Prefecture, Japan. Bosoite is
hexagonal, and it crystalises as an epitaxial intergrowth on chibaite crystals, with the
{0001} of bosoite parallel to octahedral {111} form of chibaite. Crystals are colourless
and transparent with vitreous lustre. The calculated density is 2.04 g/cm3
. The empirical
formula (based on 2 O apfu and guest molecules assumed as CH4) is
Na0.01(Si0.98Al0.02)∑1.00O2∙0.50CH4; the endmember formula is SiO2∙nCxH2x+2. Bosoite is
hexagonal, space group P6/mmm, with the unit-cell parameters a = 13.9020(3) Å, c =
11.2802(2) Å, V = 1887.99(6) Å3
and Z = 34. The crystal structure of bosoite was refined
by single-crystal X-ray diffraction and converged to R1 = 4.26% for the average model,
and R1 = 2.96% for the model where all oxygen sites are split.
Instrument
NRS-5100
Keywords
bosoite; new mineral; silica clathrate; chibaite; hydrocarbon, Japan