Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Mineralogy is an earth science that involves the chemistry, crystal structure, and physical (including optical) properties of minerals. ...

• Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. This occurs quite easily in graphite, making the material feel slippery.

• Cubic cleavage: cleavage parallel to the faces of a cube. This is the source of the cubic shape seen in crystals of ground table salt (sodium chloride).

• Diagonal cleavage: cleavage parallel to a diagonal plane.

• Lateral cleavage: cleavage parallel to the lateral planes.

• 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).

• Prismatic cleavage, cleavage parallel to a vertical Prism.

This is of technical importance in the electronics industry and in the cutting of gemstones. While precious stones are generally cleaved by impact, man-made single crystals of semiconductor materials are generally sold as thin wafers which are much easier to cleave. Simply pressing a silicon wafer against a soft surface and scratching its edge with a diamond scribe is usually enough to cause cleavage; however, when dicing a wafer to form chips, a procedure of scoring and breaking is often followed for greater control. The vast majority of commercial semiconductors (Si, Ge, GaAs, InSb, etc.) are diamond cubic, a space group for which octahedral cleavage is observed. This means that some orientations of wafer allow near-perfect rectangles to be cleaved. Graphite (named by Abraham Gottlob Werner in 1789, from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ... Three dimensions A cube (or hexahedron) is a Platonic solid composed of six square faces, with three meeting at each vertex. ... Edible salt is a mineral, one of the few rocks people eat. ... An octahedron (plural: octahedra) is a polyhedron with eight faces. ... A dodecahedron is literally a polyhedron with 12 faces, but usually a regular dodecahedron is meant: a Platonic solid composed of twelve pentagonal faces, with three meeting at each vertex. ... The n-sided trapezohedron or deltohedron is the dual polyhedron of a regular n-sided antiprism. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... A prismatic surface is a surface generated by all the lines that are parallel to a given line and intersect a broken line that is not in the same plane as the given line. ... In geometry, a prism is a polyhedron made of two parallel copies of some polygonal base joined by faces that are rectangles or parallelograms. ... The field of electronics is the study and use of systems that operate by controlling the flow of electrons (or other charge carriers) in devices such as thermionic valves and semiconductors. ... A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... An etched silicon wafer In microelectronics, a wafer is a thin slice of semiconducting material, such as a silicon crystal, upon which microcircuits are constructed by doping (for example, diffusion or ion implantation), etching, and deposition of various materials. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... For other uses, including the shape ◊, see Diamond (disambiguation). ... General Name, Symbol, Number germanium, Ge, 32 Chemical series metalloids Group, Period, Block 14, 4, p Appearance grayish white Atomic mass 72. ... This article is about the chemical compound. ... Indium antimonide (InSb) is a narrow gap semiconductor material from the group the (III-V group) used in infrared detectors, including thermal imaging cameras, FLIR systems, infrared homing missile guidance systems, and in infrared astronomy. ... One unit cell of the diamond cubic crystal structure. ... The space group of a crystal is a mathematical description of the symmetry inherent in the structure. ...

See also

• Crystal structure
• Facet
• Fracture

Rose des Sables (Sand Rose), formed of gypsum crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Facets are flat faces on geometric shapes. ... A fracture is the separation of a body into two, or more, pieces under the action of stress. ...

References

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, pp. 200 - 202, ISBN 0471805807
• Mineral galleries: Mineral properties - Cleavage