Okenite, Ca ₁₀ Si ₁₈ O ₄₆ . 18H ₂ O; the first example of a chain and sheet silicate

Univ. Pisa, Ist. Mineral. e Petrogr., Pisa, Italy

The structure is composed of the following structural units: (a) tetrahedral sheets S, with composition (Si ₆ O ₁₅ ) (super -6) , characterized by five- and eight-membered rings of silicate tetrahedra, with five tetrahedra pointing in one direction and one tetrahedron pointing in the other direction; (b) three-repeat double chains C, with composition (Si ₆ O ₁₆ ) (super -8) and characterized by four- and six-membered rings, made up by pairing two wollastonite chains, which point in opposite directions; (c) octahedral double chains O, formed by two strands of octahedra. These structural units are connected by corner sharing to give the complex layer SOCOS, with composition [Ca ₈ (Si ₆ O ₁₆ )(Si ₆ O ₁₅ ) ₂ (H ₂ O) ₆ ] (super -4) . --Modified journal abstract.

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