Cleavage , in mineralogy and materials science , is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye. If bonds in certain directions are weaker than others, the crystal will tend to split along the weakly bonded planes. These flat breaks are termed "cleavage". The classic example of cleavage is mica , which cleaves in a single direction along the basal pinacoid , making the layers seem like pages in a book. In fact, mineralogists often refer to "books of mica".
33-458: René Just Haüy ( French pronunciation: [aɥi] ) FRS MWS FRSE (28 February 1743 – 1 June 1822) was a French priest and mineralogist , commonly styled the Abbé Haüy after he was made an honorary canon of Notre Dame . Due to his innovative work on crystal structure and his four-volume Traité de Minéralogie (1801), he is often referred to as the "Father of Modern Crystallography". During
66-406: A hexagonal pattern where the covalent bonds are shorter (and thus even stronger) than those of diamond. However, each layer is connected to the other with a longer and much weaker van der Waals bond . This gives graphite a single direction of cleavage, parallel to the basal pinacoid. So weak is this bond that it is broken with little force, giving graphite a slippery feel as layers shear apart. As
99-454: A royal charter in 1783, allowing for its expansion. Around 50 new fellows are elected each year in March. As of 2016 there are around 1,650 Fellows, including 71 Honorary Fellows and 76 Corresponding Fellows. Fellows are entitled to use the post-nominal letters FRSE, Honorary Fellows HonFRSE, and Corresponding Fellows CorrFRSE. The Fellowship is split into four broad sectors, covering
132-684: A classic in the field. By then, Haüy had applied his ideas to the differentiation of different species. He systematically described all the known minerals, sorting them into classes, and giving their chemical and geometrical properties. His work, in four volumes, including an atlas of plates, was accounted among the most wonderful of the 19th century. It has been described as "a work of comprehensive insight, and much of it, written with literary fluency". A second updated edition appeared as Traité de cristallographie in 1822. Haüy created comprehensive collections containing hundreds of pear-wood models of crystal models for education and demonstrations. One such set
165-679: A collection of all Earth materials. In October 1794, René Just Haüy was appointed the first curator of the Cabinet of Mineralogy, later known as the Musée de Minéralogie . He may therefore be considered a founder of the Musée de Minéralogie. On November 9, 1794, Haüy also became a professor of physics at the École normale supérieure . In 1802, Haüy became a professor of mineralogy at the Muséum national d'Histoire naturelle (National Museum of Natural History). Haüy's work
198-515: A nearby abbey of Premonstrants . Through him, Haüy was introduced to a colleague in Paris and obtained a scholarship to the College of Navarre . Haüy eventually became an usher, and in 1764, was appointed regent (master) of the fourth class. Haüy also progressed in his religious training. He was tonsured in 1762, took minor orders in 1765, was appointed a subdeacon in 1767, became a deacon in 1769, and
231-558: A result, graphite makes an excellent dry lubricant . While all single crystals will show some tendency to split along atomic planes in their crystal structure , if the differences between one direction or another are not large enough, the mineral will not display cleavage. Corundum , for example, displays no cleavage. Cleavage forms parallel to crystallographic planes: Crystal parting occurs when minerals break along planes of structural weakness due to external stress, along twin composition planes, or along planes of weakness due to
264-450: A single fracture along one of the edges of the base, by which it had been attached to the rest of the group. Instead of placing it in the collection I was then forming, I tried to divide it in other directions, and I succeeded, after several attempts, in extracting its rhomboid nucleus." René-Just Haüy, Traité de minéralogie (1801) Studying the fragments inspired Haüy to make further experiments in crystal cutting. Breaking down crystals to
297-403: A wafer to form chips, a procedure of scoring and breaking is often followed for greater control. Elemental semiconductors ( silicon , germanium , and diamond) 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. Most other commercial semiconductors ( GaAs , InSb , etc.) can be made in
330-454: Is of technical importance in the electronics industry and in the cutting of gemstones . Precious stones are generally cleaved by impact, as in diamond cutting . Synthetic 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
363-472: The French Revolution he also helped to establish the metric system . René-Just Haüy was born at Saint-Just-en-Chaussée on February 28, 1743, in the province of Picardy (later the département of Oise ). His parents were Just Haüy, a poor linen-weaver, and his wife Magdeleine Candelot. Haüy's interest in the services and music of the local church brought him to the attention of the prior of
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#1732852170463396-610: The French Revolution , Haüy refused to take an oath accepting the Civil Constitution of the Clergy , and became a non-juring priest . He was thrown into prison after the monarchy was overthrown on August 10, 1792. Étienne Geoffroy Saint-Hilaire interceded on his behalf. Haüy was released just a few days before the September Massacres of September 2–7, 1792 in which many of the clergy were killed. On August 8, 1793, in spite of
429-549: The Légion d'Honneur . After 1814 Haüy was deprived of his appointments by the Restoration government. He spent his final days in poverty, dying in Paris on June 1, 1822, even if "June 3" is systematically reported. The confusion in Haüy's death date (June 1 instead of June 3) is an 1823 error by Cuvier , rectified in 1944 by A. Lacroix but still often misreported. In 1817, René-Just Haüy
462-486: The National Convention passed a decree, in favor of developing uniform weights and measures across France. On September 11, 1793, they established a Temporary Commission of Weights and Measures made up of twelve scientists, including Haüy, whose task was to carry out the decree. The work of the commission was disrupted by political events. In November 1793, Lavoisier and several others were arrested and removed from
495-419: The exsolution of another mineral. Parting breaks are very similar in appearance to cleavage, but the cause is different. Cleavage occurs because of design weakness while parting results from growth defects (deviations from the basic crystallographic design). Thus, cleavage will occur in all samples of a particular mineral, while parting is only found in samples with structural defects. Examples of parting include
528-507: The Commission. On May 8, 1794, Lavoisier was guillotined. Nonetheless, Haüy remained secretary of the Commission through this turmoil. The law of 18 Germinal an III was enacted on April 7, 1795, formally establishing the metric system in France. On July 12, 1794, a public decree reorganized the École des Mines (School of Mines) in Paris and specified the establishment of a Cabinet of Mineralogy,
561-642: The Royal Society's catalogue, to various scientific journals, especially the Journal de physique and the Annales du Museum d'Histoire Naturelle . FRSE Fellowship of the Royal Society of Edinburgh ( FRSE ) is an award granted to individuals that the Royal Society of Edinburgh , Scotland's national academy of science and letters , judged to be "eminently distinguished in their subject". This society received
594-488: The Society. Cleavage (crystal) Diamond and graphite provide examples of cleavage. Each is composed solely of a single element , carbon . In diamond, each carbon atom is bonded to four others in a tetrahedral pattern with short covalent bonds . The planes of weakness (cleavage planes) in a diamond are in four directions, following the faces of the octahedron . In graphite, carbon atoms are contained in layers in
627-481: The blind, the Institution des Jeunes Aveugles (Institute for Blind Youth) in Paris. An accident apparently directed René-Just Haüy's attention to what became a new field in natural history , crystallography . Haüy was examining a broken specimen of calcareous spar in the collection of Jacques de France de Croisset. (According to some accounts, Haüy dropped the specimen and caused it to break.) He became intrigued by
660-452: The development of X-Ray diffraction technology many years later, in 1902. Haüy was not the only researcher to observe that calcite crystals could be composed of smaller rhombohedra, but it was he who introduced the idea of triple periodicity in crystals. This idea was fundamental to later developments in the field on crystal lattices . Between 1784 and 1822, Haüy published more than 100 reports discussing his theories and their application to
693-607: The efforts of Antoine Lavoisier , the Académie royale des sciences de Paris was dissolved by the National Convention . It was not restored until August 22, 1795, when it became known as the Institut National des Sciences et des Arts (National Institute of Sciences and Arts). Before its suppression, the Academy of Sciences had formed a working group to develop a uniform system of weights and measures for use throughout France. Lavoisier
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#1732852170463726-551: The full range of physical and life sciences, arts, humanities, social sciences, education, professions, industry, business and public life. Examples of current fellows include Peter Higgs and Jocelyn Bell Burnell . Previous fellows have included Melvin Calvin , Benjamin Franklin , James Clerk Maxwell , James Watt , Thomas Reid , and Andrew Lawrence . A comprehensive biographical list of Fellows from 1783–2002 has been published by
759-451: The octahedral parting of magnetite , the rhombohedral and basal parting in corundum , and the basal parting in pyroxenes . Cleavage is a physical property traditionally used in mineral identification, both in hand-sized specimen and microscopic examination of rock and mineral studies. As an example, the angles between the prismatic cleavage planes for the pyroxenes (88–92°) and the amphiboles (56–124°) are diagnostic. Crystal cleavage
792-405: The perfectly smooth plane of the fracture. "The observation I have just noted is that which has served to develop my ideas on the structure of crystals. It presented itself in the case of a crystal that the citizen Defrance was kind enough to give me just after it had broken off from a group this enlightened amateur was showing me, and which formed part of his mineralogical collection. The prism had
825-611: The smallest pieces possible, Haüy concluded that each type of crystal has a fundamental primitive, nucleus or “integrant molecule” of a particular shape, that could not be broken further without destroying both the physical and chemical nature of the crystal. He further argued that crystal structures are made up of orderly arrangements of these integrant molecules in successive layers, according to geometrical laws of crystallization . Crystals that had been classed together previously were identified as being of separate mineral species if their fundamental structure differed. Heavyspar, for example,
858-513: The structure of crystalline substances. Haüy first stated his laws of decrement in Essai d'une théorie sur la structure des crystaux (1784). It was a radical departure from his previous works, introducing his theory of molé constituantes or constituent molecules. By 1792, he had identified a number of parallelepipeds as possible primitive crystal forms. Haüy worked out the mathematical theory of his work in his Traité de minéralogie (1801), which became
891-461: Was a major proponent, and on March 30, 1791, he submitted a plan on behalf of the Commission on Weights and Measures, which was adopted by the Constituent Assembly . Lavoisier and Haüy were tasked with determining the density of water. As of January 4, 1793, they determined the weight of a cubic decimeter of distilled water at the temperature of melting ice, the kilogram . On August 1, 1793,
924-567: Was acquired by Martin van Marum , curator of the Teylers Museum and a director of the Hollandsche Maatschappij der Wetenschappen . Haüy is also known for his observations on pyroelectricity . He detected pyroelectricity in calamine , an oxide of zinc , as early as 1785. He studied pyroelectricity in a number of other minerals including tourmaline and related them to crystalline structure. He showed that electricity in tourmaline
957-575: Was appreciated by Napoleon , who made Haüy an Honorary Canon of the Eglise Métropolitain de Paris ( Notre Dame ) on April 5, 1802. On November 28, 1803, Haüy became one of the first recipients of the Order of the Légion d'Honneur . Napoleon encouraged Haüy to write Traité élémentaire de physique (1803), and is reported to have read it during his incarceration on Elba in 1814. During his brief return to power in 1815, Napoleon promoted Haüy to officer of
990-424: Was differentiated into specimens containing barium and strontium . The value of Haüy's discovery was immediately recognized. Haüy and his contemporaries worked with limited evidence. They could observe a crystal's habit and cleavage planes and measure interfacial angles with an instrument called a goniometer . The internal structure underlying the crystal's integrant molecule would not be determinable until
1023-535: Was elected an honorary member of the New York Academy of Sciences . His name is the thirteenth inscribed on the south-east side of the Eiffel Tower . The mineral Haüyne was named for Haüy in 1807 by Thomas-Christophe Bruun-Neergaard. It occurs in silica-deficient igneous rocks in a wide variety of locations. The following are Haüy's principal works: He also contributed papers, of which 100 are enumerated in
René Just Haüy - Misplaced Pages Continue
1056-467: Was ordained as a Roman Catholic priest in 1770. After his ordination, Haüy became regent (teacher) of the second class at the Collège du Cardinal-Lemoine. Through his friendship with his spiritual director, Abbé Lhomond , Haüy became interested first in botany , and after hearing a lecture by Louis-Jean-Marie Daubenton , in mineralogy . His brother Valentin Haüy was the founder of the first school for
1089-536: Was strongest at the poles of the crystal and became imperceptible at the middle. Haüy published a book on electricity and magnetism, Exposition raisonné de la théorie de l'électricité et du magnétisme, d'après les principes d'Æpinus , in 1787. On February 12, 1783, Haüy was elected to the Académie royale des sciences de Paris ( French Academy of Sciences ) with the rank of an adjoint in botany, there being no vacancy in either physics or mineralogy. In 1788, he became as an associate in natural history and mineralogy. During
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