Triangular dipyramid
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In geometry, the triangular dipyramid is one of the Johnson solids (J12). As the name suggests, it can be constructed by joining two tetrahedra along one face. It is a convex deltahedron. Although all its faces are congruent and the solid is face-uniform, it is not a Platonic solid because some vertices adjoin three faces and others adjoin four.
The 92 Johnson solids were named and described by Norman Johnson in 1966.
External link
- Johnson Solid -- from MathWorld (http://mathworld.wolfram.com/JohnsonSolid.html)