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Calcite - Twinned and Untwinned Scalenohedra
Based on specimens from Ohio and Tennessee
One of the most distinctive forms that calcite takes is the scalenohedron, recognizable by its alternating pairs of faces with steeper and shallower intersections, all meeting in the center to produce an equatorial zigzag. Although there are many possible scalenohedra, ranging from squat to extremely pointy, the form {21.1} is the most common. Both of these models represent that form. One shows the scalenohedron alone, and the other shows an idealized twin of the same form on (00.1).
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Calcite - Scalenohedron with Rhombohedron Faces
Based on a specimen from Joplin, MO
The calcite crystal this model is based on has an attractive combination of forms, with the added bonus of a sharp orange phantom inside. On the surface, the faces of the rhombohedron {02.1} bevel the edges of the scalenohedron {21.1}, while the phantom appears to be the scalenohedron alone. This model shows only the surface forms, although I am contemplating the future construction of a glass or plexiglass model with a visible phantom model suspended inside.