A hemi-icosahedron is a geometric shape that can be thought of as half of a regular icosahedron. An icosahedron is a polyhedron with 20 equilateral triangular faces, 30 edges, and 12 vertices. When we talk about a "hemi" version, we typically refer to one of the two symmetrical halves that can be obtained by slicing the icosahedron through its center.
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