Illustration from 1911 Encyclopædia Britannica, article CALCITE.

Original text: The primitive rhombohedron, r {100} (fig. 1), is comparatively rare except in combination with other forms. A flatter rhombohedron, e {110}, is shown in fig. 2, and a more acute one, f {111}, in fig. 3. These three rhombohedra are related in such a manner that, when in combination, the faces of r truncate the polar edges of f, and the faces of e truncate the edges of r. The crystal of prismatic habit shown in fig. 4 is a combination of the prism m {211} and the rhombohedron e {110}; fig. 5 is a combination of the scalenohedron v {201} and the rhombohedron r {100}; and the crystal of tabular habit represented in fig. 6 is a combination of the basal pinacoid c {111}, prism m {211}, and rhombohedron e {110}.

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