An uncommon sample of a pale-blue Madagascar cordierite and its mineral inclusions of different kinds have been studied. The physical properties of the embedding cordierite are: α = 1·528, β = 1·522, γ = 1·537, δ = 0·009, 2V
= 96°, density = 2·534 g/cm3, a = 17·082 Å, b = 9·728, c = 9·352, Δ = 0·26. The electron probe analysis gave SiO2=48·64%, Al2O3 = 35·08, FeO = 0·70, MgO = 12·35, H2O+ = 2·50. This is therefore a hydrous magnesian cordierite. Its structural state is related to the shift in α, β, γ, 2V
α, and Δ with heating. Probe analyses were performed on the inclusions: hydro-xyapatite, dolomite, and rutile. The occurrence of dolomite suggests the conditions of formation of the host mineral.