Fukalite, a new calcium carbonate silicate hydrate mineral

Fukalite occurs in spurrite-gehlenite skarns at Fuka, and Mihara, Okayama Prefecture, and at Kushiro, Hiroshima Prefecture. It is an alteration product of spurrite and is associated with calcite and/or xonotlite. It is found as pale brown to white crystals up to 0.2 mm long.The crystals are orthorhombic a 5.48(1), b 3.78(1), c 23.42(3)Å, Z=2. They are optically biaxial, 2V about 90°, refractive indices α 1.595, β 1.605, γ 1.626 for the Fuka materials, elongation negative. The wet chemical analyses give an ideal formula Ca4Si2O6(OH)2(CO3). The density is 2.770 g/cm3 (observed) and 2.77 g/cm3 (calculated). The strong lines of the X-ray powder pattern are 2.854, 3.084, 2.926, 2.388, 1.756 and 5.86 Å.The mineral is named after the first locality, Fuka, Okayama Prefecture, Japan.