Bromyrite or bromargyrite is a natural mineral form of silver bromide found in Mexico and Chile. Hardness is 1.5 to 2. Related are iodyrite, it was first described in 1859 for an occurrence in Plateros, Mexico where it occurred in a silver deposit as an oxidation product of primary ore minerals. It occurs in arid environments along with native silver and smithsonite along with iron and manganese oxide minerals
Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water. Upon illumination or heating, silver chloride converts to silver, signaled by grey to black or purplish coloration to some samples. AgCl occurs as a mineral chlorargyrite. Silver chloride is synthesized by combining aqueous solutions of silver nitrate and sodium chloride. AgNO 3 + NaCl ⟶ AgCl ↓ + NaNO 3 It can be produced by reacting silver nitrate with cobalt chloride; this precipitation is general for silver nitrate's reaction with soluble chloride salts and is not unique to cobalt. 2 AgNO 3 + CoCl 2 ⟶ 2 AgCl ↓ + Co 2 The solid adopts the fcc NaCl structure, in which each Ag+ ion is surrounded by an octahedron of six chloride ligands. AgF and AgBr crystallize similarly. However, the crystallography depends on the condition of crystallization free silver ion concentration, as is shown on the pictures left. AgCl dissolves in solutions containing ligands such as chloride, triphenylphosphine, thiosulfate and ammonia.
Silver chloride reacts with these ligands according to the following illustrative equations: AgCl + Cl − ⟶ AgCl 2 − AgCl + 2 S 2 O 3 2 − ⟶ 3 − + Cl − AgCl + 2 NH 3 ⟶ Ag 2 + + Cl − Silver chloride does not react with nitric acid. Most complexes derived from AgCl are two-, three-, and, in rare cases, four-coordinate, adopting linear, trigonal planar, tetrahedral coordination geometries, respectively. In one of the most famous reactions in chemistry, addition of colorless aqueous silver nitrate to an colorless solution of sodium chloride produces an opaque white precipitate of AgCl: Ag + + Cl − ⟶ AgCl This conversion is a common test for the presence of chloride in solution. Due to its conspicuousness it is used in titration, which gives the typical case of argentometry; the solubility product, for AgCl in water is 1.77×10−10 at room temperature, which indicates that only 1.9 mg of AgCl will dissolve per liter of water. The chloride content of an aqueous solution can be determined quantitatively by weighing the precipitated AgCl, which conveniently is non-hygroscopic, since AgCl is one of the few transition metal chlorides, unreactive toward water.
Interfering ions for this test are iodide, as well as a variety of ligands. For AgBr and AgI, the Ksp values are 5.2 x 10 − 8.3 x 10 − 17, respectively. Silver bromide and silver iodide are significantly more photosensitive than is AgCl. AgCl darkens on exposure to light by disintegrating into elemental chlorine and metallic silver; this reaction is used in film. The silver chloride electrode is a common reference electrode in electrochemistry. Silver chloride's low solubility makes it a useful addition to pottery glazes for the production of "Inglaze lustre". Silver chloride has been used as an antidote for mercury poisoning, assisting in the elimination of mercury. Silver chloride is used: to make photographic paper since it reacts with photons to form latent image and via photoreduction in photochromic lenses, again taking advantage of its reversible conversion to Ag metal in bandages and wound healing products to create yellow and brown shades in stained glass manufacture as an infra-red transmissive optical component as it can be hot-
Cubic crystal system
In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most simplest shapes found in crystals and minerals. There are three main varieties of these crystals: Primitive cubic Body-centered cubic, Face-centered cubic Each is subdivided into other variants listed below. Note that although the unit cell in these crystals is conventionally taken to be a cube, the primitive unit cell is not; the three Bravais lattices in the cubic crystal system are: The primitive cubic system consists of one lattice point on each corner of the cube. Each atom at a lattice point is shared between eight adjacent cubes, the unit cell therefore contains in total one atom; the body-centered cubic system has one lattice point in the center of the unit cell in addition to the eight corner points. It has a net total of 2 lattice points per unit cell; the face-centered cubic system has lattice points on the faces of the cube, that each gives one half contribution, in addition to the corner lattice points, giving a total of 4 lattice points per unit cell.
Each sphere in a cF lattice has coordination number 12. Coordination number is the number of nearest neighbours of a central atom in the structure; the face-centered cubic system is related to the hexagonal close packed system, where two systems differ only in the relative placements of their hexagonal layers. The plane of a face-centered cubic system is a hexagonal grid. Attempting to create a C-centered cubic crystal system would result in a simple tetragonal Bravais lattice; the isometric crystal system class names, point groups, examples, International Tables for Crystallography space group number, space groups are listed in the table below. There are a total 36 cubic space groups. Other terms for hexoctahedral are: normal class, ditesseral central class, galena type. A simple cubic unit cell has a single cubic void in the center. A body-centered cubic unit cell has six octahedral voids located at the center of each face of the unit cell, twelve further ones located at the midpoint of each edge of the same cell, for a total of six net octahedral voids.
Additionally, there are 24 tetrahedral voids located in a square spacing around each octahedral void, for a total of twelve net tetrahedral voids. These tetrahedral voids are not local maxima and are not technically voids, but they do appear in multi-atom unit cells. A face-centered cubic unit cell has eight tetrahedral voids located midway between each corner and the center of the unit cell, for a total of eight net tetrahedral voids. Additionally, there are twelve octahedral voids located at the midpoints of the edges of the unit cell as well as one octahedral hole in the center of the cell, for a total of four net octahedral voids. One important characteristic of a crystalline structure is its atomic packing factor; this is calculated by assuming that all the atoms are identical spheres, with a radius large enough that each sphere abuts on the next. The atomic packing factor is the proportion of space filled by these spheres. Assuming one atom per lattice point, in a primitive cubic lattice with cube side length a, the sphere radius would be a⁄2 and the atomic packing factor turns out to be about 0.524.
In a bcc lattice, the atomic packing factor is 0.680, in fcc it is 0.740. The fcc value is the highest theoretically possible value for any lattice, although there are other lattices which achieve the same value, such as hexagonal close packed and one version of tetrahedral bcc; as a rule, since atoms in a solid attract each other, the more packed arrangements of atoms tend to be more common. Accordingly, the primitive cubic structure, with low atomic packing factor, is rare in nature, but is found in polonium; the bcc and fcc, with their higher densities, are both quite common in nature. Examples of bcc include iron, chromium and niobium. Examples of fcc include aluminium, copper and silver. Compounds that consist of more than one element have crystal structures based on a cubic crystal system; some of the more common ones are listed here. The space group of the caesium chloride structure is called Pm3m, or "221"; the Strukturbericht designation is "B2". One structure is the "interpenetrating primitive cubic" structure called the "caesium chloride" structure.
Each of the two atom types forms a separate primitive cubic lattice, with an atom of one type at the center of each cube of the other type. Altogether, the arrangement of atoms is the same as body-centered cubic, but with alternating types of atoms at the different lattice sites. Alternately, one could view this lattice as a simple cubic structure with a secondary atom in its cubic void. In addition to caesium chloride itself, the structure appears in certain other alkali halides when prepared at low temperatures or high pressures; this structure is more to be formed from two elements whose ions are of the same size. The coordination
Broken Hill is an inland mining city in the far west of outback New South Wales, Australia. It is near the border with South Australia on the crossing of the Barrier Highway and the Silver City Highway, in the Barrier Range, it is 315 m above sea level, with a hot desert climate, an average rainfall of 235 mm. The closest major city is Adelaide, the capital of South Australia, more than 500 km to the southwest and linked via route A32; the town has a high historical importance in Australia's mining and economic history after the discovery of silver ore led to the opening of various mines, thus establishing Broken Hill's recognition as a prosperous mining town well into the 1990s. Despite experiencing a slowing economic situation into the late 1990s and 2000s, Broken Hill itself was listed on the National Heritage List in 2015 and remains Australia's longest running mining town. Broken Hill has been referred to as "The Silver City", less as the "Oasis of the West", the "Capital of the Outback".
Although over 1,100 km west of Sydney and surrounded by semi-desert, the town has prominent park and garden displays and offers a number of attractions, such as the Living Desert Sculptures. The town has a high potential for solar power, given its extensive daylight hours of sunshine; the Broken Hill Solar Plant, completed in 2015, is one of the largest in the Southern Hemisphere. Unlike the rest of New South Wales, Broken Hill observes Australian Central Standard Time, the same time zone used in South Australia and the Northern Territory; this is because at the time the Australian dominions adopted standard time, Broken Hill's only direct rail link was with Adelaide, not Sydney. Broken Hill is regarded as part of South Australia for the purposes of postal parcels rates, telephone charges. Broken Hill used to be a break of gauge station where the state railway systems of South Australia and New South Wales met. Broken Hill is Australia's longest-lived mining city. In 1844, the explorer Charles Sturt saw and named the Barrier Range, at the time referred to a "Broken Hill" in his diary.
Silver ore was discovered on this broken hill in 1883 by a boundary rider named Charles Rasp. The "broken hill" that gave its name to Broken Hill comprised a number of hills that appeared to have a break in them; the broken hill no longer exists. The area was known as Willyama. Prior to Sturt's naming, the surrounding area was referred to by the local Aboriginal population as the "Leaping Crest". Broken Hill's massive orebody, which formed about 1,800 million years ago, has proved to be among the world's largest silver–lead–zinc mineral deposits; the orebody is shaped like a boomerang plunging into the earth at its ends and outcropping in the centre. The protruding tip of the orebody stood out as a jagged rocky ridge amongst undulating plain country on either side; this was known as the broken hill by early pastoralists. Miners called the ore body the Line of Lode. A unique mineral identified from Broken Hill has been named Nyholmite after Ron Nyholm. Lead with the isotope signature of the Broken Hill deposits has been found across the entire continent of Antarctica in ice cores dating back to the late nineteenth century.
The earliest human settlers in the area around Broken Hill are thought to have been the Wiljakali Indigenous Australians, once thought to have only intermittently lived in the area because of the lack of permanent water sources, but it has since been found that the Indigenous Clans of the area were able to survive on underground water holes and wells that were unknown to the European settlers. Many of these waterholes are still kept secret from non-Indigenous people; as in much of Australia, a combination of white settler disease and aggression drove them from their lands. The first whites to visit the area was Surveyor General of New South Wales, Major Thomas Mitchell, in 1841. Three years in 1844, the explorer Charles Sturt saw and named the Barrier Range while searching for an inland sea. Burke and Wills passed through the area on their famous 1860–61 expedition, setting up a base camp at nearby Menindee. Pastoralists first began settling the area in the 1850s, the main trade route to the area was along the Darling River.
Broken Hill was founded in 1883 by boundary rider Charles Rasp, who patrolled the Mount Gipps fences. In 1883 he discovered what he thought was tin; the orebody they came from proved to be the richest of its kind in the world. Rasp and six associates founded the Broken Hill Proprietary Company BHP Billiton, now BHP again, in 1885 as the Syndicate of Seven. By 1915 BHP had realised that its ore reserves were limited and begun to diversify into steel production. Mining at the BHP mines at Broken Hill ceased 28 February 1939. BHP was not the only mining operation at Broken Hill though, mining continued at the southern and northern ends of the Line of Lode; the southern and northern operations are run by Perilya Limited, who plan to open further mines along the Line of Lode. The Battle of Broken Hill took place on New Year's Day 1915 when two Afghan men fired upon a trainload of people who were headed to a New Years Day picnic. Since Australia was at war at the time with the Ottoman Empire, the men were first thought to be Turkish, but were identified as being from the British colony of India.
They killed wounded six, before they were killed by a group of policemen and soldiers. In 1918, the Italian Ambassador to Australia, Emilio Eles, with the help of the Australian p
Encyclopædia Britannica, Eleventh Edition
The Encyclopædia Britannica, Eleventh Edition is a 29-volume reference work, an edition of the Encyclopædia Britannica. It was developed during the encyclopaedia's transition from a British to an American publication; some of its articles were written by the best-known scholars of the time. This edition of the encyclopedia, containing 40,000 entries, is now in the public domain, many of its articles have been used as a basis for articles in Wikipedia. However, the outdated nature of some of its content makes its use as a source for modern scholarship problematic; some articles have special value and interest to modern scholars as cultural artifacts of the 19th and early 20th centuries. The 1911 eleventh edition was assembled with the management of American publisher Horace Everett Hooper. Hugh Chisholm, who had edited the previous edition, was appointed editor in chief, with Walter Alison Phillips as his principal assistant editor. Hooper bought the rights to the 25-volume 9th edition and persuaded the British newspaper The Times to issue its reprint, with eleven additional volumes as the tenth edition, published in 1902.
Hooper's association with The Times ceased in 1909, he negotiated with the Cambridge University Press to publish the 29-volume eleventh edition. Though it is perceived as a quintessentially British work, the eleventh edition had substantial American influences, not only in the increased amount of American and Canadian content, but in the efforts made to make it more popular. American marketing methods assisted sales; some 14% of the contributors were from North America, a New York office was established to coordinate their work. The initials of the encyclopedia's contributors appear at the end of selected articles or at the end of a section in the case of longer articles, such as that on China, a key is given in each volume to these initials; some articles were written by the best-known scholars of the time, such as Edmund Gosse, J. B. Bury, Algernon Charles Swinburne, John Muir, Peter Kropotkin, T. H. Huxley, James Hopwood Jeans and William Michael Rossetti. Among the lesser-known contributors were some who would become distinguished, such as Ernest Rutherford and Bertrand Russell.
Many articles were carried over from some with minimal updating. Some of the book-length articles were divided into smaller parts for easier reference, yet others much abridged; the best-known authors contributed only a single article or part of an article. Most of the work was done by British Museum scholars and other scholars; the 1911 edition was the first edition of the encyclopædia to include more than just a handful of female contributors, with 34 women contributing articles to the edition. The eleventh edition introduced a number of changes of the format of the Britannica, it was the first to be published complete, instead of the previous method of volumes being released as they were ready. The print type was subject to continual updating until publication, it was the first edition of Britannica to be issued with a comprehensive index volume in, added a categorical index, where like topics were listed. It was the first not to include long treatise-length articles. Though the overall length of the work was about the same as that of its predecessor, the number of articles had increased from 17,000 to 40,000.
It was the first edition of Britannica to include biographies of living people. Sixteen maps of the famous 9th edition of Stielers Handatlas were translated to English, converted to Imperial units, printed in Gotha, Germany by Justus Perthes and became part this edition. Editions only included Perthes' great maps as low quality reproductions. According to Coleman and Simmons, the content of the encyclopedia was distributed as follows: Hooper sold the rights to Sears Roebuck of Chicago in 1920, completing the Britannica's transition to becoming a American publication. In 1922, an additional three volumes, were published, covering the events of the intervening years, including World War I. These, together with a reprint of the eleventh edition, formed the twelfth edition of the work. A similar thirteenth edition, consisting of three volumes plus a reprint of the twelfth edition, was published in 1926, so the twelfth and thirteenth editions were related to the eleventh edition and shared much of the same content.
However, it became apparent that a more thorough update of the work was required. The fourteenth edition, published in 1929, was revised, with much text eliminated or abridged to make room for new topics; the eleventh edition was the basis of every version of the Encyclopædia Britannica until the new fifteenth edition was published in 1974, using modern information presentation. The eleventh edition's articles are still of value and interest to modern readers and scholars as a cultural artifact: the British Empire was at its maximum, imperialism was unchallenged, much of the world was still ruled by monarchs, the tragedy of the modern world wars was still in the future, they are an invaluable resource for topics omitted from modern encyclopedias for biography and the history of science and technology. As a literary text, the encyclopedia has value as an example of early 20th-century prose. For example, it employs literary devices, such as pathetic fallacy, which are not as common in modern reference texts.
In 1917, using the pseudonym of S. S. Van Dine, the US art critic and author Willard Huntington Wright published Misinforming a Nation, a 200+
Mohs scale of mineral hardness
The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, some of which are more quantitative; the method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c. 77 AD. While facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is relevant for field geologists, who use the scale to identify minerals using scratch kits; the Mohs scale hardness of minerals can be found in reference sheets. Mohs hardness is useful in milling, it allows assessment of.
The scale is used at electronic manufacturers for testing the resilience of flat panel display components. The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly; the samples of matter used by Mohs are all different minerals. Minerals are chemically pure solids found in nature. Rocks are made up of one or more minerals; as the hardest known occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5. "Scratching" a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye. Materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number.
While these microscopic dislocations are permanent and sometimes detrimental to the harder material's structural integrity, they are not considered "scratches" for the determination of a Mohs scale number. The Mohs scale is a purely ordinal scale. For example, corundum is twice as hard as topaz; the table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate has a hardness of 7.0. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale; the table below incorporates additional substances that may fall between levels: Comparison between hardness and hardness: Mohs hardness of elements is taken from G. V. Samsonov in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA, 1968. Cordua, William S. "The Hardness of Minerals and Rocks". Lapidary Digest, c. 1990
Jarosite is a basic hydrous sulfate of potassium and iron with a chemical formula of KFe3+362. This sulfate mineral is formed in ore deposits by the oxidation of iron sulfides. Jarosite is produced as a byproduct during the purification and refining of zinc and is commonly associated with acid mine drainage and acid sulfate soil environments. Jarosite has a trigonal crystal structure and is brittle, with basal cleavage, a hardness of 2.5-3.5, a specific gravity of 3.15-3.26. It is translucent to opaque with a vitreous to dull luster, is colored dark yellow to yellowish-brown, it can sometimes be confused with limonite or goethite with which it occurs in the gossan. Jarosite is an iron analogue of alunite; the alunite supergroup includes the alunite, beudantite and florencite subgroups. The alunite supergroup minerals are isostructural with each other and substitution between them occurs, resulting in several solid solution series; the alunite supergroup has the general formula AB326. In the alunite subgroup B is Al, in the jarosite subgroup B is Fe3+.
The beudantite subgroup has the general formula AB36, the crandallite subgroup AB 3 2 5 ⋅ H 2 O and the florencite subgroup AB325 or 6. In the jarosite-alunite series Al may substitute for Fe and a complete solid solution series between jarosite and alunite, KAl326 exists, but intermediate members are rare; the material from Kopec, Czech Republic, has about equal Fe and Al, but the amount of Al in jarosite is small. In the jarosite-natrojarosite series Na substitutes for K to at least Na/K = 1:2.4 but the pure sodium end member NaFe3+326 is not known in nature. Minerals with Na > K are known as natrojarosite. End member formation is favoured by a low temperature environment, less than 100 °C, is illustrated by the oscillatory zoning of jarosite and natrojarosite found in samples from the Apex Mine and Gold Hill, Utah; this indicates that there is a wide miscibility gap between the two end members, it is doubtful whether a complete series exists between jarosite and natrojarosite. In hydroniumjarosite the hydronium ion H3O+ can substitute for K+, with increased hydronium ion content causing a marked decrease in the lattice parameter c, although there is little change in a.
Hydroniumjarosite will only form from alkali-deficient solutions, as alkali-rich jarosite forms preferentially. Divalent cations may substitute for the monovalent cation K+ in the A site. Charge balance may be achieved in three ways. Firstly by replacing two monovalent cations by one divalent cation, leaving an A site vacancy, as in plumbogummite, Pb 2 + Al 3 2 5 ⋅ H 2 O, a member of the crandallite subgroup. Secondly by incorporating divalent ions in the B sites, as in osarizawaite, Pb2+Cu2+Al226, alunite subgroup, beaverite, Pb2+Cu2+226, jarosite subgroup. Thirdly by replacing divalent anions with trivalent anions, as in beudantite, PbFe3+33−6, beudantite subgroup. Jarosite was first described in 1852 by August Breithaupt in the Barranco del Jaroso in the Sierra Almagrera; the name jarosite is directly derived from Jara, the Spanish name of a yellow flower that belongs to the genus Cistus and grows in this sierra. The mineral and the flower have the same color. Mysterious spheres of clay 1.5 to 5 inches in diameter and covered with jarosite have been found beneath the Temple of the Feathered Serpent an ancient six level stepped pyramid 30 miles from Mexico City.
Ferric sulfate and jarosite have been detected by Opportunity. These substances are indicative of oxidizing conditions prevailing at the surface of Mars. In May 2009, the Spirit rover became stuck when it drove over a patch of soft ferric sulfate, hidden under a veneer of normal-looking soil; because iron sulfate has little cohesion, the rover's wheels could not gain sufficient traction to pull the body of the rover out of the iron sulfate patch. Multiple techniques were attempted to extricate the rover, but the wheels sank so into the iron sulfate that the body of the rover came to rest on the martian surface, preventing the wheels from exerting any force on the material below them; as the JPL team failed to recover the mobility of Spirit, it signified the end of the journey for the rover. Jarosite is a more generic term denoting an extensive family of compounds of the form AM362, where A+ = Na, K, Rb, NH4, H3O, Ag, Tl and M3+ = Fe, Cr, V. In condensed matter physics and materials science they are renowned for containing layers with kagome lattice structure, relating to geometrically frustrated magnets.
Alunite Iron sulfate Spirit Mars rover final embedding event Palache C. Berman H. and Frondel C. Dana’s system of mineralogy, v. II, 560–562. Webmineral data Cornell University How an obscure mineral provided a vital clue to Martian water. Discovery News "Robot Finds Mysterious Spheres in Ancient Temple" Further information about