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Tuesday, November 19, 2019

War crime

From Wikipedia, the free encyclopedia
 
A picture taken by the Polish Underground of Nazi Secret Police rounding up Polish intelligentsia at Palmiry near Warsaw in 1940 for mass execution (German AB-Aktion in occupied Poland).
 
A war crime is an act that constitutes a serious violation of the laws of war that gives rise to individual criminal responsibility. Examples of war crimes include intentionally killing civilians or prisoners, torturing, destroying civilian property, taking hostages, performing a perfidy, raping, using child soldiers, pillaging, declaring that no quarter will be given, and seriously violating the principles of distinction and proportionality, and military necessity

The concept of war crimes emerged at the turn of the twentieth century when the body of customary international law applicable to warfare between sovereign states was codified. Such codification occurred at the national level, such as with the publication of the Lieber Code in the United States, and at the international level with the adoption of the treaties during the Hague Conventions of 1899 and 1907. Moreover, trials in national courts during this period further helped clarify the law. Following the end of World War II, major developments in the law occurred. Numerous trials of Axis war criminals established the Nuremberg principles, such as notion that war crimes constituted crimes defined by international law. Additionally, the Geneva Conventions in 1949 defined new war crimes and established that states could exercise universal jurisdiction over such crimes. In the late 20th century and early 21st century, following the creation of several international courts, additional categories of war crimes applicable to armed conflicts other than those between states, such as civil wars, were defined.

History

Suzhou, China, 1938. A ditch full of the bodies of Chinese civilians, killed by Japanese soldiers.

Early examples

The trial of Peter von Hagenbach by an ad hoc tribunal of the Holy Roman Empire in 1474 was the first "international" war crimes trial, and also of command responsibility. He was convicted and beheaded for crimes that "he as a knight was deemed to have a duty to prevent", although he had argued that he was "just following orders"

In 1865, Henry Wirz, a Confederate States Army officer, was held accountable by a military tribunal and hanged for the appalling conditions at Andersonville Prison, where many Union prisoners of war died during the American Civil War.

Hague Conventions

The Hague Conventions were international treaties negotiated at the First and Second Peace Conferences at The Hague, Netherlands, in 1899 and 1907, respectively, and were, along with the Geneva Conventions, among the first formal statements of the laws of war and war crimes in the nascent body of secular international law.

Geneva Conventions

The Geneva Conventions are four related treaties adopted and continuously expanded from 1864 to 1949 that represent a legal basis and framework for the conduct of war under international law. Every single member state of the United Nations has currently ratified the conventions, which are universally accepted as customary international law, applicable to every situation of armed conflict in the world. However, the Additional Protocols to the Geneva Conventions adopted in 1977 containing the most pertinent, detailed and comprehensive protections of international humanitarian law for persons and objects in modern warfare are still not ratified by a number of States continuously engaged in armed conflicts, namely the United States, Israel, India, Pakistan, Iraq, Iran, and others. Accordingly, states retain different codes and values with regard to wartime conduct. Some signatories have routinely violated the Geneva Conventions in a way which either uses the ambiguities of law or political maneuvering to sidestep the laws' formalities and principles.
Three conventions were revised and expanded with the fourth one added in 1949:
  • First Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field (Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field was adopted in 1864, significantly revised and replaced by the 1906 version, the 1929 version, and later the First Geneva Convention of 1949).
  • Second Geneva Convention for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea (Convention for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea was adopted in 1906, significantly revised and replaced by the Second Geneva Convention of 1949).
  • Third Geneva Convention relative to the Treatment of Prisoners of War (Convention relative to the Treatment of Prisoners of War was adopted in 1929, significantly revised and replaced by the Third Geneva Convention of 1949).
  •  
Two Additional Protocols were adopted in 1977 with the third one added in 2005, completing and updating the Geneva Conventions:
  • Protocol I (1977) relating to the Protection of Victims of International Armed Conflicts.
  • Protocol II (1977) relating to the Protection of Victims of Non-International Armed Conflicts.
  • Protocol III (2005) relating to the Adoption of an Additional Distinctive Emblem.

Leipzig War Crimes Trial

A small number of German military personnel of the First World War were tried in 1921 by the German Supreme Court for alleged war crimes.

London Charter / Nuremberg Trials 1945

The modern concept of war crime was further developed under the auspices of the Nuremberg Trials based on the definition in the London Charter that was published on August 8, 1945. (Also see Nuremberg Principles.) Along with war crimes the charter also defined crimes against peace and crimes against humanity, which are often committed during wars and in concert with war crimes.

International Military Tribunal for the Far East 1946

Also known as the Tokyo Trial, the Tokyo War Crimes Tribunal or simply as the Tribunal, it was convened on May 3, 1946 to try the leaders of the Empire of Japan for three types of crimes: "Class A" (crimes against peace), "Class B" (war crimes), and "Class C" (crimes against humanity), committed during World War II.

International Criminal Court 2002

Bodies of some of the hundreds of Vietnamese villagers who were killed by U.S. soldiers during the My Lai Massacre.
 
On July 1, 2002, the International Criminal Court, a treaty-based court located in The Hague, came into being for the prosecution of war crimes committed on or after that date. Several nations, most notably the United States, China, Russia, and Israel, have criticized the court. The United States still participates as an observer. Article 12 of the Rome Statute provides jurisdiction over the citizens of non-contracting states in the event that they are accused of committing crimes in the territory of one of the state parties.

War crimes are defined in the statute that established the International Criminal Court, which includes:
  1. Grave breaches of the Geneva Conventions, such as:
    1. Willful killing, or causing great suffering or serious injury to body or health
    2. Torture or inhumane treatment
    3. Unlawful wanton destruction or appropriation of property
    4. Forcing a prisoner of war to serve in the forces of a hostile power
    5. Depriving a prisoner of war of a fair trial
    6. Unlawful deportation, confinement or transfer
    7. Taking hostages
    8. Directing attacks against civilians
  • The following acts as part of a non-international conflict:
    1. Murder, cruel or degrading treatment and torture
    2. Directing attacks against civilians, humanitarian workers or UN peacekeepers
  • The following acts as part of an international conflict:
    1. Civilians killed in shelling in eastern Ukraine. According to the HRW report, "The use of indiscriminate rockets in populated areas violates international humanitarian law, or the laws of war, and may amount to war crimes."
      1. Taking hostages
      2. Summary execution
      3. Pillage
      4. Rape, sexual slavery, forced prostitution or forced pregnancy
    However the court only has jurisdiction over these crimes where they are "part of a plan or policy or as part of a large-scale commission of such crimes".

    Prominent indictees

    Heads of state and government

    Sudanese President Omar al-Bashir, wanted by the ICC for war crimes and crimes against humanity.
     
    To date, the present and former heads of state and heads of government that have been charged with war crimes include:
    • German Großadmiral and President Karl Dönitz and Japanese Prime Ministers and Generals Hideki Tōjō and Kuniaki Koiso in the aftermath of World War II.
    • Former Serbian President Slobodan Milošević was brought to trial charges with, genocide, crimes against humanity, and war crimes in three republics. The tribunal found the prosecution had according to its rules and procedures; enough evidence was tailored, prior to the defense presentation, that, "a reasonable trier of fact, could conclude, the accused was responsible for the crimes charged." This pertaining to superior responsibility, for the Bosnia and Croatia indictment's, and individual responsibility, for the Kosovo indictment. No conviction was established however, as he died in custody in 2006, before the trial could be concluded.
    • Former Liberian President Charles G. Taylor was also brought to The Hague charged with war crimes; his trial stretched from 2007 to March 2011. He was convicted in April 2012 of Aiding and Abbetting and planning the commission of Crimes against Humanity, committed during the war under individual and command responsibility.
    • Former Bosnian Serb President Radovan Karadžić was arrested in Belgrade on July 18, 2008 and brought before Belgrade's War Crimes Court a few days after. He was extradited to the Netherlands, and is currently in The Hague, in the custody of the International Criminal Tribunal for the former Yugoslavia. The trial began in 2010. On March 24, 2016, he was found guilty of genocide in Srebrenica, war crimes and crimes against humanity, 10 of the 11 charges in total, and sentenced to 40 years' imprisonment. He was sentenced to life on appeal.
    • Omar al-Bashir, former head of state of Sudan, is charged with three counts of genocide, crimes against humanity and other war crimes regarding the 2003– War in the Darfur region of Sudan. The first head of state charged with genocide by the International Criminal Court with current warrants of arrest actions in Darfur.

    Other prominent indictees

    Definition

    Aftermath of the Malmedy massacre (1944).
     
    War crimes are serious violations of the rules of customary and treaty law concerning international humanitarian law that have become accepted as criminal offenses for which there is individual responsibility. Colloquial definitions of war crime include violations of established protections of the laws of war, but also include failures to adhere to norms of procedure and rules of battle, such as attacking those displaying a peaceful flag of truce, or using that same flag as a ruse to mount an attack on enemy troops. The use of chemical and biological weapons in warfare are also prohibited by numerous chemical arms control agreements and the Biological Weapons Convention. Wearing enemy uniforms or civilian clothes to infiltrate enemy lines for espionage or sabotage missions is a legitimate ruse of war, though fighting in combat or assassinating individuals behind enemy lines while so disguised is not, as it constitutes unlawful perfidy. Attacking enemy troops while they are being deployed by way of a parachute is not a war crime. However, Protocol I, Article 42 of the Geneva Conventions explicitly forbids attacking parachutists who eject from disabled aircraft and surrendering parachutists once landed. Article 30 of the 1907 Hague Convention IV – The Laws and Customs of War on Land explicitly prohibits belligerents to punish enemy spies without previous trial.

    The rule of war, also known as the Law of Armed Conflict, permit belligerents to engage in combat. A war crime occurs when superfluous injury or unnecessary suffering is inflicted upon an enemy.

    War crimes also include such acts as mistreatment of prisoners of war or civilians. War crimes are sometimes part of instances of mass murder and genocide though these crimes are more broadly covered under international humanitarian law described as crimes against humanity. In 2008, the U.N. Security Council adopted Resolution 1820, which noted that "rape and other forms of sexual violence can constitute war crimes, crimes against humanity or a constitutive act with respect to genocide"; see also war rape. In 2016, the International Criminal Court convicted someone of sexual violence for the first time; specifically, they added rape to a war crimes conviction of Congo Vice President Jean-Pierre Bemba Gombo.

    Mass grave of Soviet POWs, killed by Germans. Some 3.3 million Soviet POWs died in Nazi custody.
     
    War crimes also included deliberate attacks on citizens and property of neutral states, such as the Japanese attack on Pearl Harbor. As the attack on Pearl Harbor happened while the U.S. and Japan were at peace and without a just cause for self-defense, the attack was declared by the Tokyo Trials to go beyond justification of military necessity and therefore constituted a war crime.

    War crimes are significant in international humanitarian law because it is an area where international tribunals such as the Nuremberg Trials and Tokyo Trials have been convened. Recent examples are the International Criminal Tribunal for the Former Yugoslavia and the International Criminal Tribunal for Rwanda, which were established by the UN Security Council acting under Chapter VIII of the UN Charter.

    Under the Nuremberg Principles, war crimes are different from crimes against peace. Crimes against peace include planning, preparing, initiating, or waging a war of aggression, or a war in violation of international treaties, agreements, or assurances. Because the definition of a state of "war" may be debated, the term "war crime" itself has seen different usage under different systems of international and military law. It has some degree of application outside of what some may consider to be a state of "war", but in areas where conflicts persist enough to constitute social instability.

    The legalities of war have sometimes been accused of containing favoritism toward the winners ("Victor's justice"), as some controversies have not been ruled as war crimes. Some examples include the Allies' destruction of Axis cities during World War II, such as the firebombing of Dresden, the Operation Meetinghouse raid on Tokyo (the most destructive single bombing raid in history), and the atomic bombings of Hiroshima and Nagasaki. In regard to the strategic bombing during World War II, there was no international treaty or instrument protecting a civilian population specifically from attack by aircraft, therefore the aerial attacks on civilians were not officially war crimes. The Allies at the trials in Nuremberg and Tokyo never prosecuted the Germans, including Luftwaffe commander-in-chief Hermann Göring, for the bombing raids on Warsaw, Rotterdam, and British cities during the Blitz as well as the indiscriminate attacks on Allied cities with V-1 flying bombs and V-2 rockets, nor the Japanese for the aerial attacks on crowded Chinese cities. Although there are no treaties specific to aerial warfare, Protocol 1, Article 51 of the Geneva Conventions explicitly prohibits the bombardment of cities where civilian population might be concentrated regardless of any method.

    Controversy arose when the Allies re-designated German POWs (under the protection of the 1929 Geneva Convention on Prisoners of War) as Disarmed Enemy Forces (allegedly unprotected by the 1929 Geneva Convention on Prisoners of War), many of which then were used for forced labor such as clearing minefields. By December 1945, six months after the war had ended, it was estimated by French authorities that 2,000 German prisoners were still being killed or maimed each month in mine-clearing accidents. The wording of the 1949 Third Geneva Convention was intentionally altered from that of the 1929 convention so that soldiers who "fall into the power" following surrender or mass capitulation of an enemy are now protected as well as those taken prisoner in the course of fighting.

    Legality of Civilian Casualties

    Under the Law of Armed Conflict (LOAC), the death of non-combatants isn't necessarily a violation, there are many things to take into account. Civilians cannot be made the object of an attack, but the death/injury of civilians while conducting an attack on a military objective are governed under principles such as of proportionality and military necessity and can be permissible. Military necessity “permits the destruction of life of … persons whose destruction is incidentally unavoidable by the armed conflicts of the war; ... it does not permit the killing of innocent inhabitants for purposes of revenge or the satisfaction of a lust to kill. The destruction of property to be lawful must be imperatively demanded by the necessities of war"

    For example, conducting an operation on ammunition depot or a terrorist training camp would not be prohibited because a farmer is plowing a field in the area, the farmer is not the object of attack and the operations would adhere to proportionality and military necessity. On the other hand, an extraordinary military advantage would be necessary to justify an operation posing risks of collateral death or injury to thousands of civilians. In "grayer cases" the legal question of whether the expected incidental harm is excessive may be very subjective. For this reason, States have chosen to apply a “clearly excessive” standard for determining whether a criminal violation has occurred.

    When there is no justification for military action, such as civilians being made the object of attack, a proportionality analysis is unnecessary to conclude that the attack is unlawful.

    International Criminal Tribunal for the former Yugoslavia

    For aerial strikes, pilots generally have to rely on information supplied external sources (Headquarters, ground troops) that a specific position is in fact a military target. In the case of former Yugoslavia, NATO pilots hit a civilian object (United States bombing of the Chinese embassy in Belgrade) that was of no military significance, but the pilots had no idea of determining it aside from their orders. The committee ruled that "the aircrew involved in the attack should not be assigned any responsibility for the fact they were given the wrong target and that it is inappropriate to attempt to assign criminal responsibility for the incident to senior leaders because they were provided with wrong information by officials of another agency.". The report also notes that "Much of the material submitted to the OTP consisted of reports that civilians had been killed, often inviting the conclusion to be drawn that crimes had therefore been committed. Collateral casualties to civilians and collateral damage to civilian objects can occur for a variety of reasons." 

    Rendulic Rule

    The Rendulic Rule is a standard by which commanders are judged.

    German General Lothar Rendulic was charged for ordering extensive destruction of civilian buildings and lands while retreating a suspected enemy attack in what is called scorched earth policy for the military purpose of denying the use of ground for the enemy. He overestimated the perceived risk but argued that Hague IV authorized the destruction because if it's necessary to war. He was acquitted of that charge.

    Under the "Rendulic Rule" persons must assess the military necessity of an action based on the information available to them at that time; they cannot be judged based on information that subsequently comes to light.

    Monday, November 18, 2019

    Quartz

    From Wikipedia, the free encyclopedia
     
    Quartz
    Quartz, Tibet.jpg
    Quartz crystal cluster from Tibet
    General
    Categoryoxide mineral
    Formula
    (repeating unit)
    SiO2
    Strunz classification4.DA.05 (Oxides)
    Dana classification75.01.03.01 (tectosilicates)
    Crystal systemα-quartz: trigonal
    β-quartz: hexagonal
    Crystal classα-quartz: trapezohedral (class 3 2); β-quartz: trapezohedral (class 6 2 2)
    Unit cella = 4.9133 Å, c = 5.4053 Å; Z=3
    Identification
    Formula mass60.083 g·mol−1
    ColorColorless through various colors to black
    Crystal habit6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive
    TwinningCommon Dauphine law, Brazil law and Japan law
    Cleavage{0110} Indistinct
    FractureConchoidal
    TenacityBrittle
    Mohs scale hardness7 – lower in impure varieties (defining mineral)
    LusterVitreous – waxy to dull when massive
    StreakWhite
    DiaphaneityTransparent to nearly opaque
    Specific gravity2.65; variable 2.59–2.63 in impure varieties
    Optical propertiesUniaxial (+)
    Refractive indexnω = 1.543–1.545
    nε = 1.552–1.554
    Birefringence+0.009 (B-G interval)
    PleochroismNone
    Melting point1670 °C (β tridymite) 1713 °C (β cristobalite)
    SolubilityInsoluble at STP; 1 ppmmass at 400 °C and 500 lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2
    Other characteristicslattice: hexagonal, Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic)

    Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. The atoms are linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.

    Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at 573 °C (846 K). Since the transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature threshold.

    There are many different varieties of quartz, several of which are semi-precious gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia.

    Etymology

    The word "quartz" is derived from the German word "Quarz", which had the same form in the first half of the 14th century in Middle High German in East Central German and which came from the Polish dialect term kwardy, which corresponds to the Czech term tvrdý ("hard").

    The Ancient Greeks referred to quartz as κρύσταλλος (krustallos) derived from the Ancient Greek κρύος (kruos) meaning "icy cold", because some philosophers (including Theophrastus) apparently believed the mineral to be a form of supercooled ice. Today, the term rock crystal is sometimes used as an alternative name for the purest form of quartz.

    Crystal habit and structure

    Quartz mineral embedded in limestone (top right of the sample), easily identifiable by its hexagonal form. It cannot be scratched by steel (see Mohs scale).
     
    Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often twinned (with twin right-handed and left-handed quartz crystals), distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals typically form in a 'bed' that has unconstrained growth into a void; usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, for instance within gypsum. A quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.

    α-quartz crystallizes in the trigonal crystal system, space group P3121 or P3221 depending on the chirality. β-quartz belongs to the hexagonal system, space group P6222 and P6422, respectively. These space groups are truly chiral (they each belong to the 11 enantiomorphous pairs). Both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks (SiO4 tetrahedra in the present case). The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, without change in the way they are linked.

    Varieties (according to microstructure)

    Although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties.

    Major varieties of quartz
    Type Color & Description Transparent
    Herkimer diamond Colorless Transparent
    Rock crystal Colorless Transparent
    Amethyst Purple to violet colored quartz Transparent
    Citrine Yellow quartz ranging to reddish orange or brown, and occasionally greenish yellow Transparent
    Ametrine A mix of amethyst and citrine with hues of purple/violet and yellow or orange/brown Transparent
    Rose quartz Pink, may display diasterism Transparent
    Chalcedony Fibrous, variously translucent, cryptocrystalline quartz occurring in many varieties.
    The term is often used for white, cloudy, or lightly colored material intergrown with moganite.
    Otherwise more specific names are used.

    Carnelian Reddish orange chalcedony Translucent
    Aventurine Quartz with tiny aligned inclusions (usually mica) that shimmer with aventurescence Translucent to opaque
    Agate Multi-colored, curved or concentric banded chalcedony (cf. Onyx) Semi-translucent to translucent
    Onyx Multi-colored, straight banded chalcedony or chert (cf. Agate) Semi-translucent to opaque
    Jasper Opaque cryptocrystalline quartz, typically red to brown but often used for other colors Opaque
    Milky quartz White, may display diasterism Translucent to opaque
    Smoky quartz Light to dark gray, sometimes with a brownish hue Translucent to opaque
    Tiger's eye Fibrous gold, red-brown or bluish colored chalcedony, exhibiting chatoyancy.
    Prasiolite Mint green Transparent
    Rutilated quartz Contains acicular (needle-like) inclusions of rutile
    Dumortierite quartz Contains large amounts of dumortierite crystals

    Varieties (according to color)

    Quartz crystal demonstrating transparency
     
    Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, and has often been used for hardstone carvings, such as the Lothair Crystal. Common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. These color differentiations arise from chromophores which have been incorporated into the crystal structure of the mineral. Polymorphs of quartz include: α-quartz (low), β-quartz, tridymite, moganite, cristobalite, coesite, and stishovite.

    The most important distinction between types of quartz is that of macrocrystalline (individual crystals visible to the unaided eye) and the microcrystalline or cryptocrystalline varieties (aggregates of crystals visible only under high magnification). The cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a cryptocrystalline form of silica consisting of fine intergrowths of both quartz, and its monoclinic polymorph moganite. Other opaque gemstone varieties of quartz, or mixed rocks including quartz, often including contrasting bands or patterns of color, are agate, carnelian or sard, onyx, heliotrope, and jasper.

    Amethyst

    Amethyst is a form of quartz that ranges from a bright vivid violet to dark or dull lavender shade. The world's largest deposits of amethysts can be found in Brazil, Mexico, Uruguay, Russia, France, Namibia and Morocco. Sometimes amethyst and citrine are found growing in the same crystal. It is then referred to as ametrine. An amethyst is formed when there is iron in the area where it was formed.

    Blue quartz

    Blue quartz contains inclusions of fibrous magnesio-riebeckite or crocidolite.

    Dumortierite quartz

    Inclusions of the mineral dumortierite within quartz pieces often result in silky-appearing splotches with a blue hue, shades giving off purple and/or grey colors additionally being found. "Dumortierite quartz" (sometimes called "blue quartz") will sometimes feature contrasting light and dark color zones across the material. Interest in the certain quality forms of blue quartz as a collectible gemstone particularly arises in India and in the United States.

    Citrine

    Citrine is a variety of quartz whose color ranges from a pale yellow to brown due to ferric impurities. Natural citrines are rare; most commercial citrines are heat-treated amethysts or smoky quartzes. However, a heat-treated amethyst will have small lines in the crystal, as opposed to a natural citrine's cloudy or smokey appearance. It is nearly impossible to differentiate between cut citrine and yellow topaz visually, but they differ in hardness. Brazil is the leading producer of citrine, with much of its production coming from the state of Rio Grande do Sul. The name is derived from the Latin word citrina which means "yellow" and is also the origin of the word "citron". Sometimes citrine and amethyst can be found together in the same crystal, which is then referred to as ametrine. Citrine has been referred to as the "merchant's stone" or "money stone", due to a superstition that it would bring prosperity.

    Citrine was first appreciated as a golden-yellow gemstone in Greece between 300 and 150 BC, during the Hellenistic Age. The yellow quartz was used prior to that to decorate jewelry and tools but it was not highly sought after.

    Milky quartz

    Milk quartz or milky quartz is the most common variety of crystalline quartz. The white color is caused by minute fluid inclusions of gas, liquid, or both, trapped during crystal formation, making it of little value for optical and quality gemstone applications.

    Rose quartz

    Rose quartz is a type of quartz which exhibits a pale pink to rose red hue. The color is usually considered as due to trace amounts of titanium, iron, or manganese, in the material. Some rose quartz contains microscopic rutile needles which produces an asterism in transmitted light. Recent X-ray diffraction studies suggest that the color is due to thin microscopic fibers of possibly dumortierite within the quartz.

    Additionally, there is a rare type of pink quartz (also frequently called crystalline rose quartz) with color that is thought to be caused by trace amounts of phosphate or aluminium. The color in crystals is apparently photosensitive and subject to fading. The first crystals were found in a pegmatite found near Rumford, Maine, USA and in Minas Gerais, Brazil.

    Smoky quartz

    Smoky quartz is a gray, translucent version of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque. Some can also be black. The translucency results from natural irradiation creating free silicon within the crystal.

    Prasiolite

    Prasiolite, also known as vermarine, is a variety of quartz that is green in color. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, but it is also seen in Lower Silesia in Poland. Naturally occurring prasiolite is also found in the Thunder Bay area of Canada. It is a rare mineral in nature; most green quartz is heat-treated amethyst.

    Synthetic and artificial treatments

    A synthetic quartz crystal grown by the hydrothermal method, about 19 cm long and weighing about 127 grams
     
    Not all varieties of quartz are naturally occurring. Some clear quartz crystals can be treated using heat or gamma-irradiation to induce color where it would not otherwise have occurred naturally. Susceptibility to such treatments depends on the location from which the quartz was mined.

    Prasiolite, an olive colored material, is produced by heat treatment; natural prasiolite has also been observed in Lower Silesia in Poland. Although citrine occurs naturally, the majority is the result of heat-treating amethyst or smoky quartz. Carnelian is widely heat-treated to deepen its color.

    Because natural quartz is often twinned, synthetic quartz is produced for use in industry. Large, flawless, single crystals are synthesized in an autoclave via the hydrothermal process; emeralds are also synthesized in this fashion.

    Like other crystals, quartz may be coated with metal vapors to give it an attractive sheen.

    Occurrence

    Granite rock in the cliff of Gros la Tête on Aride Island, Seychelles. The thin (1–3 cm wide) brighter layers are quartz veins, formed during the late stages of crystallization of granitic magmas. They are sometimes called "hydrothermal veins".
     
    Quartz is a defining constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale. It is a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Quartz has the lowest potential for weathering in the Goldich dissolution series and consequently it is very common as a residual mineral in stream sediments and residual soils.

    While the majority of quartz crystallizes from molten magma, much quartz also chemically precipitates from hot hydrothermal veins as gangue, sometimes with ore minerals like gold, silver and copper. Large crystals of quartz are found in magmatic pegmatites. Well-formed crystals may reach several meters in length and weigh hundreds of kilograms.

    Naturally occurring quartz crystals of extremely high purity, necessary for the crucibles and other equipment used for growing silicon wafers in the semiconductor industry, are expensive and rare. A major mining location for high purity quartz is the Spruce Pine Gem Mine in Spruce Pine, North Carolina, United States. Quartz may also be found in Caldoveiro Peak, in Asturias, Spain.

    The largest documented single crystal of quartz was found near Itapore, Goiaz, Brazil; it measured approximately 6.1×1.5×1.5 m and weighed 39,916 kilograms.

    Related silica minerals

    Tridymite and cristobalite are high-temperature polymorphs of SiO2 that occur in high-silica volcanic rocks. Coesite is a denser polymorph of SiO2 found in some meteorite impact sites and in metamorphic rocks formed at pressures greater than those typical of the Earth's crust. Stishovite is a yet denser and higher-pressure polymorph of SiO2 found in some meteorite impact sites. Lechatelierite is an amorphous silica glass SiO2 which is formed by lightning strikes in quartz sand.

    History

    The word "quartz" comes from the German About this soundQuarz, which is of Slavic origin (Czech miners called it křemen). Other sources attribute the word's origin to the Saxon word Querkluftertz, meaning cross-vein ore.

    Quartz is the most common material identified as the mystical substance maban in Australian Aboriginal mythology. It is found regularly in passage tomb cemeteries in Europe in a burial context, such as Newgrange or Carrowmore in Ireland. The Irish word for quartz is grianchloch, which means 'sunstone'. Quartz was also used in Prehistoric Ireland, as well as many other countries, for stone tools; both vein quartz and rock crystal were knapped as part of the lithic technology of the prehistoric peoples.

    While jade has been since earliest times the most prized semi-precious stone for carving in East Asia and Pre-Columbian America, in Europe and the Middle East the different varieties of quartz were the most commonly used for the various types of jewelry and hardstone carving, including engraved gems and cameo gems, rock crystal vases, and extravagant vessels. The tradition continued to produce objects that were very highly valued until the mid-19th century, when it largely fell from fashion except in jewelry. Cameo technique exploits the bands of color in onyx and other varieties.

    Roman naturalist Pliny the Elder believed quartz to be water ice, permanently frozen after great lengths of time. (The word "crystal" comes from the Greek word κρύσταλλος, "ice".) He supported this idea by saying that quartz is found near glaciers in the Alps, but not on volcanic mountains, and that large quartz crystals were fashioned into spheres to cool the hands. This idea persisted until at least the 17th century. He also knew of the ability of quartz to split light into a spectrum.

    In the 17th century, Nicolas Steno's study of quartz paved the way for modern crystallography. He discovered that regardless of a quartz crystal's size or shape, its long prism faces always joined at a perfect 60° angle.

    Quartz's piezoelectric properties were discovered by Jacques and Pierre Curie in 1880. The quartz oscillator or resonator was first developed by Walter Guyton Cady in 1921. George Washington Pierce designed and patented quartz crystal oscillators in 1923. Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927.

    Efforts to synthesize quartz began in the mid nineteenth century as scientists attempted to create minerals under laboratory conditions that mimicked the conditions in which the minerals formed in nature: German geologist Karl Emil von Schafhäutl (1803–1890) was the first person to synthesize quartz when in 1845 he created microscopic quartz crystals in a pressure cooker. However, the quality and size of the crystals that were produced by these early efforts were poor.

    By the 1930s, the electronics industry had become dependent on quartz crystals. The only source of suitable crystals was Brazil; however, World War II disrupted the supplies from Brazil, so nations attempted to synthesize quartz on a commercial scale. German mineralogist Richard Nacken (1884–1971) achieved some success during the 1930s and 1940s. After the war, many laboratories attempted to grow large quartz crystals. In the United States, the U.S. Army Signal Corps contracted with Bell Laboratories and with the Brush Development Company of Cleveland, Ohio to synthesize crystals following Nacken's lead. (Prior to World War II, Brush Development produced piezoelectric crystals for record players.) By 1948, Brush Development had grown crystals that were 1.5 inches (3.8 cm) in diameter, the largest to date. By the 1950s, hydrothermal synthesis techniques were producing synthetic quartz crystals on an industrial scale, and today virtually all the quartz crystal used in the modern electronics industry is synthetic.

    Piezoelectricity

    Some types of quartz crystals have piezoelectric properties; they develop an electric potential upon the application of mechanical stress. An early use of this property of quartz crystals was in phonograph pickups. One of the most common piezoelectric uses of quartz today is as a crystal oscillator. The quartz clock is a familiar device using the mineral. The resonant frequency of a quartz crystal oscillator is changed by mechanically loading it, and this principle is used for very accurate measurements of very small mass changes in the quartz crystal microbalance and in thin-film thickness monitors.

    Lie group

    From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Lie_group In mathematics , a Lie gro...