抄録
The natural analogue of gehlenite hydrate synthesized by Carlson (1964) was found as an alteration product of gehlenite from Fuka, Okayama Prefecture, Japan, and as a crust on wollastonite from Carneal, Northern Ireland.
The chemical analyses of the impure Fuka material substantiate the validity of Carlson's formula 2CaO•Al2O3•SiO2H2O with minor substitution of AlAl by MgSi. X-ray powder patterns are indexed on a body-centred cubic cell with a=8.829±0.002Å (Fuka), 8.82±0.01Å (Carneal), 8.837±0.002Å (synthetic material). The strongest lines of the Fuka mineral are: 3.60 (90) (211), 2.786 (100) (310), 2.547 (30) (222), 2.354 (35) (321), 2.079 (40) (411), 1.599 (50) (440), 1.514 (25) (530). The unit cell contains 4 molecules of 2CaO•Al2O3•SiO2•H2O (Ca2Al2SiO7•H2O).
Bicchulite is white or gray in colour. The hardness could not be measured because of its powdery nature. Colourless and isotropic in thin section. The index of refraction is n=1.625 for the Carneal specimen and 1.628 for the synthetic material. The observed specific gravity is 2.75 for the synthetic material and 2.813 calculated for the synthetic material.
The name is for Bicchu, another spelling of Bitchu [bit∫u:], the name of the town including type locality in Japan.
