rhombohedra's Usage Examples:

It forms colourless, transparent rhombohedra, like those of Iceland spar; the angles are nearly equal to right angles, being 73° 30', so that the crystals look like cubes: hence the name of "cubic saltpetre.

Aluminium fluoride, AlF 3, obtained by dissolving the metal in hydrofluoric acid, and subliming the residue in a current of hydrogen, forms transparent, very obtuse rhombohedra, which are insoluble in water.

"It crystallizes in glistening rhombohedra, melting at 70°-80° C.

The Helena crystals are of tabular habit, being composed of the basal pinacoid with a very short hexagonal prism, whilst at Yogo Gulch many of the crystals affect a rhombohedral habit.

It forms a lustrous, nearly black crystalline mass, composed of minute rhombohedra.

They all crystallize in the monoclinic system, often, however, in forms closely resembling those of the rhombohedral or orthorhombic systems.

The faces of these two rhombohedra exhibit differences in surface characters, those of r being usually brighter in lustre than those of z; further, the former often predominate in size (figs.

Hot or dilute cold solutions deposit minute orthorhombic crystals of aragonite, cold saturated or moderately strong solutions, hexagonal (rhombohedral) crystals of calcite.

6° the mass becomes doubly refracting, and from a solution rhombohedral (optically uniaxial) crystals are deposited; by further cooling acicular rhombic crystals are produced at 82.

"Siderite, or spathic iron ore, FeCO 3, crystallizes in the rhombohedral system and contains 48.

It crystallizes in glistening rhombohedra, melting at 70°-80° C.

Siderite, or spathic iron ore, FeCO 3, crystallizes in the rhombohedral system and contains 48.

Although bismuth is readily obtained in fine crystals by artificial means, yet natural crystals are rare and usually indistinct: they belong to the rhombohedral system and a cube-like rhombohedron with interfacial angles of 92° 20' is the predominating form.