Apatite, the most common phosphate mineral, is generally described by the formula Ca5(PO 4) 3(OH,F,Cl) or, more completely with regard to its usual description in P63/m symmetry, by the unit cell content [Ca4][Ca6][(PO ...
Pyroxenes of pigeonitic and augitic bulk compositions in H3-4 chondritic meteorites commonly exhibit sigmoidal precipitates, rather than the elsewhere common lamellar associations. Most often, submicrometric sigmoids with ...