What is a truncation in mineralogy ?
Truncation : definition
In mineralogy, a truncation is the replacement of an edge or vertex of a polyhedron of a given crystal system by a crystal face. The truncations make it possible to obtain all the possible forms of a crystal system.
Truncated sphalerite tetrahedron
Truncated sphalerite tetrahedron
Truncated sphalerite tetrahedron