Abstract

A new pyroxenoid minerai, cascandite, with the ideal formula CaScSi3O8(0H), is triclinic with a = 9.791(8)Å, b = 10.420(9)Å, c = 7.076(6)Å, α = 98.91(8)°, β = 102.63(8)°, γ = 84.17(8)°; Z = 4 for the C1 unit cell setting. The crystal structure of cascandite is similar to those of pectolite and serandite and is composed of two main structural units: octahedral chains and three-repeat tetrahedral chains. Cascandite, unlike pectolite and serandite, has only two octahedral cations per formula unit, and the octahedral chains are formed by two strands of edge-sharing octahedra occupied by calcium and scandium cations.

Cascandite is a member of the hydrous pyroxenoid series, whose peculiarities are related to the presence of intrachain hydrogen bonding.

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