Columbite

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Columbite, an iron-niobium oxide, in this rather gorgeous miniature, forms a blocky prism with myriads of millimetre scale mini-prisms adhering to its two opposite broad faces. The crystal is opaque metallic black with what appears to be a cleaved base but could be a variant form of a matt lustre face, indicated by concentric growth patterns. The pinacoid termination is perfectly flat and mirror smooth. From Minas Gerais State in Brazil, a really excellent example of a Columbite crystal.\n