Cation sites in pyroxenoids may be classified into two groups; those in one group has been designated as M1
i (
i=0, 1, 2,···), and those in the other as M2
j (
j=1, 2, ···). The configuration of silicate chains is mainly controlled by the size of cations at M1
i. The proposed notation has much advantage in discussing crystal chemistry of pyroxenoids because in a given structural series, octahedra (or polyhedra) about sites having the same symbol share, regardless of structural type, geometrical features in common.
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