{{no footnotes, date=April 2009 Macle is a term used in

crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The wor ...

. It is a

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

form, twin-crystal or double

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

(such as

chiastolite Chiastolite ( ) is a variety of the mineral andalusite with the chemical composition Al2SiO5. It is noted for distinctive cross-shaped black inclusions of graphite. The presence of the cross caused this mineral be used as a gem. Chiastolite spe ...

). It is crystallographic twin according to the

spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties S ...

twin law and is seen in

octahedral In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...

crystals or

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

s such as

diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...

and spinel. The twin law name comes from the fact that is commonly observed in the mineral spinel. ''Macle'' is an

old French Old French (, , ; Modern French: ) was the language spoken in most of the northern half of France from approximately the 8th to the 14th centuries. Rather than a unified language, Old French was a linkage of Romance dialects, mutually intelligib ...

word, a

heraldic Heraldry is a discipline relating to the design, display and study of armorial bearings (known as armory), as well as related disciplines, such as vexillology, together with the study of ceremony, rank and pedigree. Armory, the best-known branc ...

term for a voided

lozenge Lozenge or losange may refer to: * Lozenge (shape), a type of rhombus *Throat lozenge, a tablet intended to be dissolved slowly in the mouth to suppress throat ailments *Lozenge (heraldry), a diamond-shaped object that can be placed on the field of ...

(one

shape within another). Etymologically the word is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''macula'' meaning spot,

mesh A mesh is a barrier made of connected strands of metal, fiber, or other flexible or ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands. Types * A plastic mesh may be extruded, oriented, ex ...

, or hole.

Bibliography

* Georges Friedel (1904) "Étude sur les groupements cristallins", ''Extrait du Bulletin de la Société de l'Industrie minérale'', Quatrième série, Tomes III e IV. Saint-Étienne, Société de l’Imprimerie Théolier J. Thomas et C., 485 pp. * Georges Friedel (1920) "Contribution à l'étude géométrique des macles", ''Bulletin de la Société française de Minéralogie'' 43: 246-295. * Georges Friedel (1926) ''Leçons de Cristallographie'', Berger-Levrault, Nancy, Paris, Strasbourg XIX+602 pp. * Georges Friedel (1933) "Sur un nouveau type de macles", ''Bulletin de la Société française de Minéralogie'' 56: 262-274. * J.D.H. Donnay (1940) "Width of Albite-Twinning Lamellae", ''Am. Mineral.'', 25: 578-586.

Bibliography

See also