Crystallography. Of crystalline forms: Derivative, not primitive.

Having trapeziform lateral faces in two rows between the two bases, as a crystal of barium sulphate.

contained by thirty faces, esp. by thirty rhombs, as a crystal.

having eighteen faces occupying the positions of those of three different rhomboids.

(of a crystal) having eight prismatic faces parallel to the central axis and five faces at each pyramidal end.

(of a crystal) having eight prismatic faces parallel to the central axis and six faces at each pyramidal end.

(of a crystal) having eight prismatic faces parallel to the central axis and eight faces at each pyramidal end.

designating a crystal having thirty facets arranged in five groups, each of six facets, running round the crystal.

Crystallography and Chemistry. Of or relating to an octahedron; (of a lattice site, coordination compound, etc.) having the sixfold internal…

Geometry and Crystallography. Applied to a solid figure with triangular faces, or having some other relation to a triangle. Also, Having a…

Of the nature of or relating to a pinacoid; = pinacoid, n.; spec. designating a triclinic crystal form having a centre of symmetry; (of cleavage)…

see quot.

pertaining to or having the form of a trisoctahedron.

having one quarter of the number of normals belonging to the hexagonal system.

said of a form in which only one fourth of the origin-planes are extant.