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Auguste Michel-Lévy
Auguste Michel-Lévy (7 August 184427 September 1911) was a French geologist. He was born in Paris. Biography He became inspector-general of mines, and director of the Geological Survey of France. He was distinguished for his researches on extrusive rocks and their microscopic structure and origins. He employed the polarizing microscope early on for the identification of minerals.Auguste MICHEL-LEVY (1844–1911) Annales.org In his many contributions to scientific journals he described the granulite group, and dealt with s, varioli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paris
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of cities in the European Union by population within city limits, fourth-most populous city in the European Union and the List of cities proper by population density, 30th most densely populated city in the world in 2022. Since the 17th century, Paris has been one of the world's major centres of finance, diplomacy, commerce, culture, Fashion capital, fashion, and gastronomy. Because of its leading role in the French art, arts and Science and technology in France, sciences and its early adoption of extensive street lighting, Paris became known as the City of Light in the 19th century. The City of Paris is the centre of the Île-de-France region, or Paris Region, with an official estimated population of 12,271,794 inhabitants in January 2023, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feldspar
Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldspars and the ''alkali'' (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth's crust and 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are also found in many types of sedimentary rocks. Etymology The name ''feldspar'' derives from the German , a compound of the words ' ("field") and ("flake"). had long been used as the word for "a rock easily cleaved into flakes"; was introduced in the 18th century as a more specific term, referring perhaps to its comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scientists From Paris
A scientist is a person who researches to advance knowledge in an area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engaged in the philosophical study of nature called natural philosophy, a precursor of natural science. Though Thales ( 624–545 BC) was arguably the first scientist for describing how cosmic events may be seen as natural, not necessarily caused by gods,Frank N. Magill''The Ancient World: Dictionary of World Biography'', Volume 1 Routledge, 2003 it was not until the 19th century that the term ''scientist'' came into regular use after it was coined by the theologian, philosopher, and historian of science William Whewell in 1833. History The roles of "scientists", and their predecessors before the emergence of modern scientific disciplines, have evolved considerably over time. Scientists of different eras (and before them, natural philosophers, mathematici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1911 Deaths
Events January * January 1 – A decade after federation, the Northern Territory and the Australian Capital Territory are added to the Commonwealth of Australia. * January 3 ** 1911 Kebin earthquake: An earthquake of 7.7 Moment magnitude scale, moment magnitude strikes near Almaty in Russian Turkestan, killing 450 or more people. ** Siege of Sidney Street in London: Two Latvian people, Latvian anarchists die, after a seven-hour siege against a combined police and military force. Home Secretary Winston Churchill arrives to oversee events. * January 4 – Comparison of the Amundsen and Scott expeditions, Amundsen and Scott expeditions: Robert Falcon Scott's British Terra Nova Expedition, ''Terra Nova'' Expedition to the South Pole arrives in the Antarctic and establishes a base camp at Cape Evans on Ross Island. * January 5 – Egypt's Zamalek SC is founded as a general sports and Association football club by Belgian lawyer George Merzbach as Q ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1844 Births
In the Philippines, 1844 had only 365 days, when Tuesday, December 31 was skipped as Monday, December 30 was immediately followed by Wednesday, January 1, 1845, the next day after. The change also applied to Caroline Islands, Guam, Marianas Islands, Marshall Islands and Palau as part of the Captaincy General of the Philippines; these became the first places on Earth to redraw the International Date Line. Events January–March * January 4 – The first issue of the Swedish-languaged ''Saima'' newspaper founded by J. V. Snellman is published in Kuopio, Finland. * January 15 – The University of Notre Dame, based in the city of the same name, receives its charter from Indiana. * February 27 – The Dominican Republic gains independence from Haiti. * February 28 – A gun on the USS ''Princeton'' explodes while the boat is on a Potomac River cruise, killing U.S. Secretary of State Abel Upshur, U.S. Secretary of the Navy Thomas Walker Gilmer and four other people. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porphyry (geology)
Porphyry ( ) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass. In its non-geologic, traditional use, the term ''porphyry'' usually refers to the purple-red form of this stone, valued for its appearance, but other colours of decorative porphyry are also used such as "green", "black" and "grey". The term ''porphyry'' is from the Ancient Greek (), meaning " purple". Purple was the colour of royalty, and the Roman "imperial porphyry" was a deep purple igneous rock with large crystals of plagioclase. Some authors claimed the rock was the hardest known in antiquity. Thus porphyry was prized for monuments and building projects in Imperial Rome and thereafter. Subsequently, the name was given to any igneous rocks with large crystals. The adjective ''porphyritic'' now refers to a certain texture of igneous rock regardless of its chemical and miner ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Esterellite
Esterellite (or Estérellite) is a porphyritic variety of quartz-bearing Diorite, microdiorite, containing phenocrysts of quartz, zoned andesine, and hornblende only found in the southern part of the Massif de l'Esterel, Esterel massif, between Agay and Saint-Raphaël, Var, Saint-Raphael, France. It is a bluish-grey rock, sometimes greenish, dotted with white Plagioclase Feldspar, plagioclase feldspar and Amphibole, amphibiole crystals, forming a thick laccolithic complex near Le Drammont. This volcanic rock, also known as the blue Porphyry (geology), porphyry of Estérel, was named by the French geologist Auguste Michel-Lévy, Auguste Michel-Levy in 1896. The Romans used it as paving materials but also for decorative purposes. Today, it is mainly used to make riprap, such as blocks for the dykes of the ports of Saint-Raphaël and Fréjus, railway ballast and road gravel. Structure and composition Esterellite is a porphyritic rock, completely crystalline, containing large phen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference Colour Chart
In optical mineralogy, an interference colour chart, also known as the Michel-Levy chart, is a tool first developed by Auguste Michel-Lévy to identify minerals in thin section using a petrographic microscope. With a known thickness of the thin section, minerals have specific and predictable colours in cross-polarized light, and this chart can help identify minerals. The colours are produced by the difference in speed in the fast and slow rays, also known as ''birefringence''. Usage When using the chart, it is important to remember these tips: *Isotropic and opaque (metallic) minerals cannot be identified this way. *The stage of the microscope should be rotated until maximum colour is found, and therefore, the maximum birefringence. *Each mineral, depending on the orientation, may not exhibit the maximum birefringence. It is important to sample a number of similar minerals in order to get the best value of birefringence. *Uniaxial minerals can look isotropic (always extinct) if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petrographic Microscope
A petrographic microscope is a type of optical microscope used to identify Rock (geology), rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology which focuses on detailed descriptions of rocks. The method includes aspects of polarized light microscopy (PLM). __TOC__ Description Depending on the grade of observation required, petrographic microscopes are derived from conventional Bright-field microscopy, brightfield microscopes of similar basic capabilities by: * Adding a Nicol prism polarizer filter to the light path beneath the sample slide * Replacing the normal stage with a circular rotating stage (typically graduated with vernier scales for reading orientations to better than 1 degree of arc) * Adding a second rotatable and removable Nicol prism filter, called the analyzer, to the light path between objective and eyepiece * Adding a phase telescope, also known as a Bertrand lens, which allows the viewer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thin Section
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a thin slice of a rock or mineral sample, prepared in a laboratory, for use with a polarizing petrographic microscope, electron microscope and electron microprobe. A thin sliver of rock is cut from the sample with a diamond saw and ground optically flat. It is then mounted on a glass slide and then ground smooth using progressively finer abrasive grit until the sample is only 30 μm thick. The method uses the Michel-Lévy interference colour chart to determine thickness, typically using quartz as the thickness gauge because it is one of the most abundant minerals. When placed between two polarizing filters set at right angles to each other, the optical properties of the minerals in the thin section alter the colour and intensity of the light as seen by the viewer. As different minerals have different optical properties, most rock forming minerals can be easily identified. Plagioclase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birefringence
Birefringence, also called double refraction, is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are described as birefringent or birefractive. The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by Danish scientist Rasmus Bartholin in 1669, who observed it in Iceland spar (calcite) crystals which have one of the strongest birefringences. In the 19th century Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
