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The chemical formula for Native Arsenic is indicated by As or Elemental Arsenic. Arsenic is actually classified under the Elemental mineral class in the field of optical mineralogy. Arsenic is a chemical element with symbol As and an atomic number 33 in the periodic table of elements. In the year 1250, Element Arsenic was believed as first isolated by Albert the Great or Albertus Magnus (1193-1280). In the year 1649, Johann Schröder was the first to publish two ways of preparing arsenic. In mid 18th century, people used Arsenic in small dozes as medicines. Arsenic was also once used to dope racehorses. In the 19th century, a sheele’s green copper arsenate was used as a coloring agent in sweets. In the 20th century, lead hydrogen arsenate has been used as an insecticide on fruit trees, which may sometimes cause brain damage to those working sprayers. During these times, arsenic was mainly used for medicinal purposes. There are several other applications and uses of arsenic. The name Arsenic was derived from the Persian work zarnikh, which means yellow orpiment. Zarnikh on the other hand was derived from a Greek word arsekon. Arsenic was frequently used for poisoning leading to murder during the Ancient times. Because of this arsenic poisoning, Arsenic has been called the Poison of Kings and the King of Poisons. In the Victorian era, vinegar and chalk are mixed with ‘arsenic’, a colourless, crystalline, soluble white arsenic, and eaten by women to improve their facial complexion and making their skin appear paler. Arsenic was also rubbed into the faces and arms of women to improve their complexion. Arsenic is commonly known to crystallize in a trigonal system of crystal formation.

 

            Specimens of Native Arsenic are usually found in shade of tin-white when viewed in reflected light of petrographic polarizing microscope used in the field of optical mineralogy. But this color will quickly tarnish to dark gray or black, which can be seen more visible when viewed with the aid of petrographic polarizing microscope used in optical mineralgy. Elemental arsenic is found in many solid forms: the yellow form is soft, waxy and unstable, and is made of tetrahedral As4 molecules similar to the molecules of white phosphorus. This yellow form of Arsenic can exhibit interesting microscope image when viewed with the aid of polarizing microscope for mineralogists. Arsenic commonly exhibits a metallic luster when specimen is viewed in reflected light of petrographic polarizing microscope for mineralogists. But this will readily become dull if specimens tarnished. When Arsenic specimens are evaluated between crossed nicols of polarizing microscopes for mineralogists, the cleavage found is commonly perfect in one direction. But this basal cleavage is rarely visible. Thus, there must be several adjustments done on the aperture diaphragm of the petrographic polarizing microscope used in the field of optical mineralogy in order to find any possible relief. Arsenic is most commonly found showing uneven fracture when specimen is viewed closely with the aid of polarized light microscope. In the field of optical mineralogy, fracture describes how a mineral breaks when broken contrary to its natural cleavage planes. Arsenic is also known as brittle semiconductor. Arsenic is most commonly found leaving a black streak when specimens are rubbed on a white streak plate. The hardness measure for Arsenic when specimen is evaluated using the Mohs scale method is usually found ranging from 3 to 4. The specific gravity measure of Arsenic gives values, which are ranging from 5.4 grams per cubic centimeters to 5.9 grams per cubic centimeters that are considered somewhat heavy for metallic minerals. The density of the yellow form is 1.97 grams per cubic centimeters while rhombohedral gray arsenic is much denser with a density of 5.73 grams per cubic centimeters. The other metalloidal forms are similarly dense.

 

            Arsenic crystals are usually found in opaque appearance. A Crystal habit of Arsenic as described in the field of optical mineralogy commonly includes pseudocubic rhombohedral crystals. The gray, black or metallic forms have somewhat layered crystal structures with bonds extending throughout the crystal. This habit can be seen more clearly displayed when specimen is evaluated under a petrographic polarizing light microscope used in the field of optical mineralogy. There is rare orthorhombic arsenic found in Saxony, Germany and it was named Arsenolamprite. This is isomorphous with Arsenic for they have the same chemistry but only differ in crystal structure. Arsenic crystals may be also found in splendid acicular radial aggregates when specimens are viewed in reflected light of polarizing microscope for mineralogists. Arsenic crystals are most commonly found in fine-grained masses with concentric bands or botryoidal crusts that are more clearly exhibited in reflected light of polarized microscopes used in the field of optical mineralogy. There are three known metalloid forms of Arsenic, of which have different crystal structures and are usually found in nature. These are the minerals pararsenolamprite, arsenic sensu strictu and the much rare arsenolamprite. Arsenic can actually bond readily to itself. Through this, Arsenic can actually form different structures like the As-As pairs in the red sulfide realgar, as an example, and the square ions in the arsenide skutterudite.

 

            Arsenic is known as a notoriously poisonous metalloid. It can occur in many allotropic forms such as yellow if molecular non-metallic and some gray or black forms if a metalloid, which is considerably rare in occurrence. Arsenic and Arsenic compounds are used in various alloys, as herbicides, pesticides and insecticides. Soluble arsenic compounds in sub toxic doses act as stimulants. When Arsenic is heated in air, it readily oxidizes to Arsenic trioxide. Its fumes from this reaction are very similar to that of the garlic odor. Arsenic and some arsenic compounds can also sublime upon heating, converting directly to a gaseous form without an intervening liquid state. Arsenic and all of its compounds are poisonous but the toxicity varies. Inorganic arsenic or arsenic combined with oxygen, chlorine or sulfur is thought to be the most toxic, while most organic forms of arsenic are relatively less toxic. Several hundreds of Arsenides or Arsenate compounds in mineral forms are known. In its solid state, arsenic appears as a silver-gray, brittle semi-metal that tarnishes in the air. Scherbencobalt is one of the obscure variety names for the concentrically banded or shelly arsenic. Arsenic is considered nearly indistinguishable from native antimony. There is some Arsenic, which contains some Antimony in its structure. Arsenic is commonly associated with silver, cinnabar, dyscrasite, nickeline and barite. Best field indicators of Arsenic usually includes color, tarnish, softness, garlic smell, density, crystal habit and it association with other minerals. Arsenic has notable occurrences in types of localities that include Saxony and Harz Mountains, Germany; England; Vosges, France; Italy and Santa Cruz Co., Arizona in the United States; Kongsberg, Norway; Honshu, Japan; and also in New Jersey in United States.



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Tuesday, March 31st, 2009 at 7:52 am
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The Native Elements Mineral Class
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