Octahedral

Octahedral cleavage - Type of cleavage exhibited on minerals of the isometric system that crystallize as octahedrons. The method of cleavage is that flat, triangular "wedges" peel off of the existing octahedron. Example = Fluorite.

Octahedral, Dodecahedral, or Rhombohedral cleavage: cleavage parallel to the faces of an octahedron, dodecahedron, or rhombohedron (respectively). Octahedral cleavage is seen in common semiconductors (see below).

Octahedral (4 cleavage planes) Prismatic (2 cleavage planes / 3rd direction shows fracture) Pinacoidal (1 cleavage plane / other two directions show fracture - produces flat sheets) Common Fracture Patterns ...

Octahedral: A geometric object with eight plane surfaces. Oiling: The process of applying mineral oil to a stone, such as an emerald, to mask inclusions and enhance the color.

Trioctahedral: Annite (Potassium Iron Aluminum Silicate Hydroxide) Aspidolite (Sodium Magnesium Aluminum Silicate Hydroxide) Biotite (Potassium Magnesium Iron Aluminum Silicate Hydroxide Fluoride) ...

Perfect octahedral crystals are sometimes set into jewelry in their original uncut octahedral shapes. The Burmese refer to these gems as nat thwe, meaning spirit polished. Sometimes nat thwe spinels will receive a very light polishing.

Figure 8. Octahedral diamond crystal, 2.6 cm, from Mbuji-Mayi, Congo. Crystal Classics specimen; Jeff Scovil photo.

Isometric; octahedral, dodecahedral, cubic ...often distorted as nuggets Envronment: veins in hydrothermal deposits, and hydrothermal replacements ...

Just like the trisoctahedral form, this form is most often seen on diamond, where it is thought to represent a solution form derived from an octahedron, not true crystallization.

Cleavage: perfect, octahedral (4 directions) Specific Gravity: 3.514 - 3.518 R.I.: 2.4175 in sodium light; one of the highest R.I.s of any gem material.

The triangular shape is the result of the octahedral crystalline structure that makes up a diamond, as the face of the octahedral form is a triangle.

85-carat diamond, yellowish, slightly spotted, but of almost perfect octahedral shape.

Individual copper crystals may may be of cubic, dodecahedral, tetrahedral, and very rarely of octahedral shape. Aggregates of crystals may be wiry in habit or form a dendritic, arborescent branching structure.

It forms predominately in cubes, pyritohedrons, sometimes octahedral and more rarely, distorted octahedral crystals. It is also seen in the druzy formation and often as inclusions inside quartz.

Spinel is a very hard semi-precious stone composed of octahedral crystals. Spinel ranges in color from red to black to yellow, frequently resembling rubies. Iron and chrome are components of spinel, giving it its color.

Hard as it is, diamond splits readily in certain definite directions (parallel to any of the triangular faces of the octahedral crystal).

The style of cutting a diamond (or other transparent gemstone) by removing the natural points of an octahedral crystal, ...

In andalusite, the Al octahedral chains are also linked by alternating Al octahedra and Si tetrahedra in a 3-D lattice.

Spinel: Probably named from the Latin word "spina", (meaning "thorn"), for its pointed crystals, spinel is a hard mineral with octahedral crystals occurring in igneous and carbonate rocks.

Diamonds can be cut and polished only with other diamonds, and only because of slight directional differences in hardness and a perfect octahedral cleavage. While diamonds are tough, they can be chipped along sharp girdles or facet edges.

GALENA - Leadhills. Intergrown cubo-octahedral xtls. to 2cms. CALCITE - New Glencrieff Mine, Wanlockhead. A 25mm scalenohedral crystal speckled with pyrite crystal inclusions.

Danalite: A mineral that occurs in octahedral crystals that is reddish in color. Dangle Earring: An earring that dangles below the ear lobe. Dark Stone: A rhinestone that has turned black or dark gray in color.

Spinel is a hard semi-precious stone composed of octahedral magnesium aluminum oxide crystals. Spinel occurs in all colors, frequently resembling and being mistaken for rubies and sapphires. Hardness 8.0, S.G.=3.6, R.I.=1.718.

This is due to the fact that the best crystals often occur in flattened octahedral and twinned stones. Due to the absence of color zoning and dichroism in spinels, recutting them is not a difficult task and is often worth while.

Danalite: A reddish mineral composed of iron, zinc manganese, glucinum and sulphur occurring in massive octahedral crystals. Danalite is named after James Dwight Dana.

Cleavage The tendency of a diamond to split along the grain parallel to one of its octahedral natural crystal faces.

Crystal Habit Crystal Habit is a consistent pattern that certain solids form. Common examples include Acicular, Dodecahedral, Octahedral, Platy, Prismatic, and Tabular.

A simple, obsolete cut with one "slice" cleaved or polished from (usually) an octahedral. forming a table as on a modern stone. Table Facet The top and largest facet on most diamonds including brilliant cuts.

crystal arrangement is one in which the crystal essentially expands outward at the same rate in all directions during its initial growth; the ideal result, when the crystal forms without any interference, is a pure and perfectly formed octahedral ...

See also: Crystal, Mineral, Minerals, Color, Gemstone