The determination and refinement of the crystal structure of yugawaralite

Yugawaralite is monoclinic, a = 6.73, b = 13.96, c = 10.02 A, {3 = 111030', space group Pc, and Z = 2 for ideal composition CaAhSi6016 . 4H20. Refinement of the structure of yugawaralite by least-squares technique yields a discrepancy index, R, of .14 and a weighted R of .13. The structure of yugawaralite is characterized by four-membered ring groups approximately perpendicular to the c axis, by five-membered ring groups at about 650 to either side of the ac plane, and by eight-membered ring groups which form channels parallel to the a and c axes. The axes of these channels lie on planes parallel to the ac plane at distances of approximately