Sharp yellow roedderite crystals from this classic German locality. From: Bellerberg, Ettringen, Eifel Mountains, Germany. — Photo: David Hospital · CC BY-SA 4.0
Roedderite
Roedderite is an IMA-recognized mineral species in the silicate class, with the chemical formula KNaMg₂(Mg₃Si₁₂)O₃₀.
It crystallizes in the hexagonal crystal system (space group P6/mcc). It is a member of the Milarite structural group.
Key properties: specific gravity 2.6; Vitreous luster; optically uniaxial.
IMA symbol Rdr, IMA status: approved, named in 1965.
Found in vesicles in contact metamorphosed basement gneiss xenoliths in leucite tephrite (Bellerberg volcano, Germany); an accessory mineral in an enstatite chondrite (Indarch meteorite).
It is found associated with Hematite, tridymite, sanidine, spinel, pyroxene, quartz, sillimanite (Bellerberg volcano, Germany); enstatite, clinoenstatite, troilite, nickel-iron.
The name refers to Dr. Edwin Woods Roedder (1919{), mineralogist, U.S. Geological Survey, who noted the synthetic compound.