Cleavage is usually in three directions parallel to the rhombohedron form.
From the en.wikipedia.org
Instead, vanadium avoids this collapse by changing to a rhombohedron.
From the sciencedaily.com
Amongst other allegorical symbols, the picture includes a magic square, and a truncated rhombohedron.
From the en.wikipedia.org
It is special by being a cuboid and a rhombohedron.
From the en.wikipedia.org
However, two regular tetrahedra can be combined with an octahedron, giving a rhombohedron that can tile space.
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More examples
A parallelepiped bounded by six similar faces (either rhombuses or parallelograms)
In geometry, a rhombohedron is a three-dimensional figure like a cube, except that its faces are not squares but rhombi. It is a special case of a parallelepiped where all edges are the same length.