Commercial bone china microstructures are far from equilibrium consisting of distinct regions of lath-like (0·4–10 μm) anorthite and spheroidal (1–3 μm) β-tricalcium phosphate (β-TCP) nodules embedded in a heterogeneous composition glass along with isolated irregular (≤30 μm) α-quartz crystals. The composition and morphology of the phases formed on firing suggest that anorthite crystallised in clay relicts by the reaction of metakaolin with CaO, β-TCP crystallised from decomposition of bone ash, and that the liquid formed on vitrification has variable composition depending on the composition of adjacent phases. P₂ O₅was never detected in the glass suggesting that any P₂ O₅ that dissolves in the liquid on firing is transient. The cracks sometimes observed in and around β-TCP clusters arise from thermal expansion mismatch between β-TCP and the surrounding glass and anorthite.