Ixiolite-(Mn2+)-Ixiolite-(Fe2+) Series, Albite (Var: Cleavelandite)
Helen Beryl Mine, Fourmile, Custer Mining District, Custer County, South Dakota, USA
2.2 x 1.7 x 1.3 cm. An exceptional example of this rare, complex tantalum oxide. A black-brown, blocky, pseudo-orthorhombic, prismatic crystal of ixiolite associated with pinkish (iron-stained) albite, var. cleavelandite. The crystal is terminated and displays two complete and one partially exposed prism faces with the other prism and lower ...
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