General Formula: W_0-1X₂Y₅Z₈O₂₂(OH, F, Cl)₂

W: 10-12 fold site (A1 site) - Na⁺, Ca²⁺ - coordination with OH^- in some cases

X: 6-8 fold site (M4 site) Ca²⁺, Na⁺, Mn²⁺, Fe²⁺, Mg²⁺, Li⁺

Y: 6 fold site (M1, M2, M3 possibilites) - Mg²⁺, Fe²⁺, Fe³⁺, Al³⁺, Ti⁴⁺ (only Ca can't fit here)

• M2 is a normal octahedral site coordinated to oxygens only
• M1 & M3 are only slightly distorted, coordinated to both oxygens & hydroxyls (usually 4 O's and 2 OH's or F)

Z: typical tetrahedral - 4-fold site - usually Si⁴²⁺, Al³⁺ - rarely anything else

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