rhombohedral

a. (Geom. & Crystallog.) Related to the rhombohedron; presenting the form of a rhombohedron, or a form derivable from a rhombohedron; relating to a system of forms including the rhombohedron and scalenohedron. [ 1913 Webster ]

Rhombohedral iron ore (Min.) See Hematite. --
Rhombohedral system (Crystallog.), a division of the hexagonal system embracing the rhombohedron, scalenohedron, etc. [ 1913 Webster ]