Two specimens of hydrous alkali-earth rare-earth aluminum phosphate from Eocene marl in southeastern Alabama have compositions approximating RAl3(PO4)2(F,OH)5(H2O)3 and R0.8Al4.6(PO4)2(F,OH)10(H2O)0.3 respectively; the x-ray diffraction pattern of each is that of the alunite-plumbogummite-beudantite group. The mineral is isotropic, with n about 1.61, d about 3.09. No explanation of the difference in composition is offered; it is noted that the other recorded analyses of similar minerals show similar differences.

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