Rhombohedral adj. (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.
Rhombohedral iron ore (Min.) See Hematite.
Rhombohedral system (Crystallog.), a division of the hexagonal system embracing the rhombohedron, scalenohedron, etc.
... hexagonal system—called also the rhombohedral—is different from the others in having four axes, three of them equal and in one plane and all at 120 deg. to each other; the fourth axis is not always equal to these three. It may be, and often is, longer or shorter. It passes through the intersecting point of the three ... — The Chemistry, Properties and Tests of Precious Stones • John Mastin
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