Crystallography. A set of triangular faces that meet in a point.

A form or crystal of a hemihedral type.

A twelve-sided polyhedron with pentagonal faces, which is particularly common in crystals of pyrite.

Crystallography. A polyhedron bounded by forty-eight equal scalene triangles; = hexoctahedron, n. b. Now disused.

Crystallography. = pyritohedron, n. Now rare.

(in the monoclinic system) a prism with faces parallel to the vertical axis.

(in the monoclinic system) a pyramid for which the ratio of the intercepts made on the ortho- and clino-axes is greater than the corresponding…

a prism made of a series of prisms of the same shape but different (transparent) materials with their bases contiguous, used to demonstrate the…

a pyramid corresponding to a macroprism.

Physical Chemistry. A fibrous crystalline structure formed in some flowing or agitated polymer solutions, consisting of many plate-like crystallites…