Redefinition of angastonite, CaMgAl<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>4</sub> ⋅ 7H<sub>2</sub>O, as an amorphous mineral

Abstract. A reinvestigation of the type angastonite specimen from Penrice marble quarry, South Australia, shows that published powder X-ray diffraction pattern for mineral corresponds to a mixture crystalline phases plus an amorphous phase. The formula mineral, CaMgAl2(PO4)2(OH)4⋅7H2O, has been found correspond proposal redefinition as phase approved by IMA CNMNC. Amorphous is isotropic with index refraction in range 1.33 1.40 and measured density 1.57(2) g cm−3. It formed incongruent leaching minyulite circulating Mg- Ca-bearing solutions. undergoes local recrystallisation form penriceite two other new crandallite-derivative layer phases. cluster model structure proposed based on crandallite-type segments. brief review minerals given.