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A solid bounded by eight faces. The regular octahedron is contained by eight equal equilateral triangles.

A combination of a cube and octahedron, esp. one in which the octahedral faces meet at the middle of the cubic edges.

A solid having forty-eight equal triangular faces.

A trigonal trisoctahedron.

ometric system bounded by twenty-four equal faces, three corresponding to each face of an octahedron. Tetragonal trisoctahedron, a trisoctahedron each face of which is a quadrilateral; called also trapezohedron and icositetrahedron. -- Trigonal trisoctahedron, a trisoctahedron each face of which is an isosceles triang…

A mineral relating to the zeolites, usually occurring in square prisms or octahedrons with pearly luster on the cleavage surface. It is a hydrous silicate of calcium and potassium.

es the diamond, the hardest of known substances, occuring in monometric crystals like the octahedron, etc. Another modification is graphite, or blacklead, and in this it is soft, and occurs in hexagonal prisms or tables. When united with oxygen it forms carbon dioxide, commonly called carbonic acid, or carbonic oxide,…

Octahedral, Dodecahedral, or Rhombohedral, cleavage, cleavage parallel to the faces of an octahedron, dodecahedron, or rhombohedron. -- Prismatic cleavage, cleavage parallel to a vertical prism.

Presenting a combination of a cube and an octahedron.

lid bounded by twenty-four similar quadrilateral faces. It is a hemihedral form of the hexoctahedron.

pair on each of its edges; or as in the case of a tetrahedron, which is hemihedral to an octahedron, it being contained under four of the planes of an octahedron. -- Hem`i*he"dral*ly, adv.

A twenty-four-sided solid; a tetragonal trisoctahedron or trapezohedron.

The trapezohedron or tetragonal trisoctahedron; -- so called as being the form of the mineral leucite.

Having eight faces or sides; of, pertaining to, or formed in, octahedrons; as, octahedral cleavage. Octahedral borax (Chem.), borax obtained from a saturated solution in octahedral crystals, which contain five molecules of water of crystallization; distinguished from common or prismatic borax. -- Octahedral iron ore (…

bodies, the five regular geometrical solids; namely, the tetrahedron, hexahedron or cube, octahedron, dodecahedron, and icosahedron. -- Platonic love, a pure, spiritual affection, subsisting between persons of opposite sex, unmixed with carnal desires, and regarding the mind only and its excellences; -- a species of l…

A niobate of calcium, cerium, and other bases, occurring usually in octahedrons of a yellowish or brownish color and resinous luster; -- so called from its becoming grass-green on being subjected to heat under the blowpipe.

ons. There are five regular polyhedrons, -- the tetrahedron, the hexahedron, or cube, the octahedron, the dodecahedron, and the icosahedron. -- Regular sales (Stock Exchange), sales of stock deliverable on the day after the transaction. -- Regular troops, troops of a standing or permanent army; -- opposed to militia.…

A mineral of a hyacinth or honey-yellow color, occuring in square octahedrons. It is an antimonate of calcium.

A mineral occuring in octahedrons of great hardness and various colors, as red, green, blue, brown, and black, the red variety being the gem spinel ruby. It consist essentially of alumina and magnesia, but commonly contains iron and sometimes also chromium.

A solid bounded by twenty-four equal and similar trapeziums; a tetragonal trisoctahedron. See the Note under Trisoctahedron.