Retzian-(Nd) is a new mineral from the Sterling Hill Mine in Ogdensburg, New Jersey. It is orthorhombic, Pban, with a = 5.690, b = 12.12, and c = 4.874Å. The dominant rare earth is Nd and the ideal formula is Mn2Nd[(OH)4AsO4]. Retzian-(Nd) occurs as euhedral crystals with forms {001}, {010}, {150}, {130}, {110}, {201}, and {021}, and is elongate parallel to [100], Optically, retzian-(Nd) is biaxial (+) with refractive indices α = 1.774, β = 1.782, and γ = 1.798 (all ±0.002); 2Vz = 69(1)° measured, 71° calculated; dispersion is weak r < v. Retzian-(Nd) is found with rhodochrosite, willemite, sonolite, calcite, barite and chloro-phoenicite in three separate parageneses at Sterling Hill.

Retzian is re-examined and redefined as Mn2Ce[(OH)4AsO4] with Ce > Nd > La, based on microprobe analysis of type material. The data presented here confirm the proposed crystal structure.

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