Hemimorphite, is Zn42·H2O, a component of calamine. It is a sorosilicate mineral, mined from the upper parts of zinc and lead ores, chiefly associated with smithsonite, ZnCO3, they were assumed to be the same mineral and both were classed under the same name of calamine. In the second half of the 18th century it was discovered that these two different minerals were both present in calamine, they resemble each other. The silicate was the rarer of the two, was named hemimorphite, because of the hemimorph development of its crystals; this unusual form, typical of only a few minerals, means that the crystals are terminated by dissimilar faces. Hemimorphite most forms crystalline crusts and layers massive, granular and reniform aggregates, concentrically striated, or finely needle-shaped, fibrous or stalactitic, fan-shaped clusters of crystals; some specimens show strong green fluorescence in shortwave ultraviolet light and weak light pink fluorescence in longwave UV. Hemimorphite most occurs as the product of the oxidation of the upper parts of sphalerite bearing ore bodies, accompanied by other secondary minerals which form the so-called iron cap or gossan.
Hemimorphite is an important ore of zinc and contains up to 54.2% of the metal, together with silicon and hydrogen. The crystals are sharp at the other; the regions on the Belgian-German border are well known for their deposits of hemimorphite of metasomatic origin Vieille Montagne in Belgium and Aachen in Germany. Other deposits are in Tarnowskie Góry area in Poland. Further hemimorphite occurrences are the Padaeng deposit near Mae Sod in western Thailand. Hurlbut, Cornelius S.. A. Aversa, G. and Balassone, G. 2003, The "Calamine" of southwest Sardinia: Geology and stable isotope geochemistry of supergene Zn mineralization: Economic Geology, v. 98, p. 731-748. Reynolds, N. A. Chisnall, T. W. Kaewsang, K. Keesaneyabutr, C. and Taksavasu, T. 2003, The Padaeng supergene nonsulfide zinc deposit, Mae Sod, Thailand: Economic Geology, v. 98, p. 773-785. Mineral galleries
Calamine is a historic name for an ore of zinc. The name calamine was derived from lapis calaminaris, a Latin corruption of Greek cadmia, the old name for zinc ores in general; the name of the Belgian town of Kelmis, La Calamine in French, home to a zinc mine, comes from that. In the 18th and 19th centuries large ore mines could be found near the German village of Breinigerberg. During the early 19th century it was discovered that what had been thought to be one ore was two distinct minerals: Zinc carbonate ZnCO3 or smithsonite and Zinc silicate Zn4Si2O72·H2O or hemimorphite. Although chemically and crystallographically quite distinct, the two minerals exhibit similar massive or botryoidal external form and are not distinguished without detailed chemical or physical analysis; the first person to separate the minerals was the British chemist and mineralogist James Smithson in 1803. In the mining industry the term calamine has been used to refer to both minerals indiscriminately. In mineralogy calamine is no longer considered a valid term.
It has been replaced by smithsonite and hemimorphite in order to distinguish it from the pinkish mixture of zinc oxide and iron oxide used in calamine lotion. In the 16th century demand for latten in England came from the needs of wool-carding, for which brass-wire combs were preferred, battery pieces The only known method for producing the alloy was by heating copper and calamine together in the cementation process and in 1568 a royal charter was granted to the Society of the Mineral and Battery Works to search for the mineral and produce brass, to reduce dependence on imported metal from Germany. Factories to exploit the process were established at Rotherhithe. By the late 17th century enough was known of metallic zinc to make brass solder directly by combining copper and spelter. In 1738 a patent was granted to William Champion, a Bristol brass founder, for the large-scale reduction of calamine to produce spelter. In 1684 a paper presented to the Royal Society touched on the medicinal and veterinary properties of the compound when in finely powdered form
In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how fast light propagates through the material. It is defined as n = c v, where c is the speed of light in vacuum and v is the phase velocity of light in the medium. For example, the refractive index of water is 1.333, meaning that light travels 1.333 times as fast in vacuum as in water. The refractive index determines how much the path of light is bent, or refracted, when entering a material; this is described by Snell's law of refraction, n1 sinθ1 = n2 sinθ2, where θ1 and θ2 are the angles of incidence and refraction of a ray crossing the interface between two media with refractive indices n1 and n2. The refractive indices determine the amount of light, reflected when reaching the interface, as well as the critical angle for total internal reflection and Brewster's angle; the refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is v = c/n, the wavelength in that medium is λ = λ0/n, where λ0 is the wavelength of that light in vacuum.
This implies that vacuum has a refractive index of 1, that the frequency of the wave is not affected by the refractive index. As a result, the energy of the photon, therefore the perceived color of the refracted light to a human eye which depends on photon energy, is not affected by the refraction or the refractive index of the medium. While the refractive index affects wavelength, it depends on photon frequency and energy so the resulting difference in the bending angle causes white light to split into its constituent colors; this is called dispersion. It can be observed in prisms and rainbows, chromatic aberration in lenses. Light propagation in absorbing materials can be described using a complex-valued refractive index; the imaginary part handles the attenuation, while the real part accounts for refraction. The concept of refractive index applies within the full electromagnetic spectrum, from X-rays to radio waves, it can be applied to wave phenomena such as sound. In this case the speed of sound is used instead of that of light, a reference medium other than vacuum must be chosen.
The refractive index n of an optical medium is defined as the ratio of the speed of light in vacuum, c = 299792458 m/s, the phase velocity v of light in the medium, n = c v. The phase velocity is the speed at which the crests or the phase of the wave moves, which may be different from the group velocity, the speed at which the pulse of light or the envelope of the wave moves; the definition above is sometimes referred to as the absolute refractive index or the absolute index of refraction to distinguish it from definitions where the speed of light in other reference media than vacuum is used. Air at a standardized pressure and temperature has been common as a reference medium. Thomas Young was the person who first used, invented, the name "index of refraction", in 1807. At the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers; the ratio had the disadvantage of different appearances. Newton, who called it the "proportion of the sines of incidence and refraction", wrote it as a ratio of two numbers, like "529 to 396".
Hauksbee, who called it the "ratio of refraction", wrote it as a ratio with a fixed numerator, like "10000 to 7451.9". Hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1. Young did not use a symbol for the index of refraction, in 1807. In the next years, others started using different symbols: n, m, µ; the symbol n prevailed. For visible light most transparent media have refractive indices between 1 and 2. A few examples are given in the adjacent table; these values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, as is conventionally done. Gases at atmospheric pressure have refractive indices close to 1 because of their low density. All solids and liquids have refractive indices above 1.3, with aerogel as the clear exception. Aerogel is a low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the other end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, but some high-refractive-index polymers can have values as high as 1.76.
For infrared light refractive indices can be higher. Germanium is transparent in the wavelength region from 2 to 14 µm and has a refractive index of about 4. A type of new materials, called topological insulator, was found holding higher refractive index of up to 6 in near to mid infrared frequency range. Moreover, topological insulator material are transparent; these excellent properties make them a type of significant materials for infrared optics. According to the theory of relativity, no information can travel faster than the speed of light in vacuum, but this does not mean that the refractive index cannot be lower than 1; the refractive index measures the phase velocity of light. The phase velocity is the speed at which the crests of the wave move and can be faster than the speed of light in vacuum, thereby give a refractive index below 1; this can occur close to resonance frequencies, for absorbing media, in plasmas, for X-rays. In the X-ray regime the refractive indices are
James Smithson, MA, FRS was an English chemist and mineralogist. He published numerous scientific papers for the Royal Society during the late 1700s as well as assisted in the development of calamine, which would be renamed after him as "smithsonite", he was the founding donor of the Smithsonian Institution, which bears his name. Born in Paris, France as the illegitimate child of Hugh Percy, the 1st Duke of Northumberland, he was given the French name Jacques-Louis Macie, his birth date was not recorded and the exact location of his birth is unknown. Shortly after his birth he naturalized to Britain where his name was anglicized to James Louis Macie, he attended university at Pembroke College, Oxford in 1782 graduating with a B. A. in 1786. As a student he participated in numerous geological expeditions and studied chemistry and mineralogy. At the age of twenty-two, he adopted his father's surname of Smithson and travelled extensively throughout Europe, publishing papers about his findings. Considered a talented amateur in his field, Smithson maintained an inheritance he acquired from his mother and other relatives.
Smithson never had no children. If his nephew were to die without heirs, Smithson's will stipulated that his estate be used "to found in Washington, under the name of the Smithsonian Institution, an establishment for the increase and diffusion of knowledge among men." In 1835, his nephew so could not claim to be the recipient of his estate. C. despite having never visited the United States. He died in Genoa, Italy on 27 June 1829, aged 64. James Smithson was born in c. 1765 to Hugh Percy, 1st Duke of Northumberland and Elizabeth Hungerford Keate Macie. His mother was the widow of a wealthy man from Weston, Bath. An illegitimate child, Smithson was born in secret in Paris, resulting in his birth name being the Francophone Jacques-Louis Macie. After the death of his parents, he changed his last name to Smithson, the surname of his biological father prior to marriage, he was educated and naturalised in England. In 1766, his mother inherited from the Hungerford family of Studley, where her brother had lived up until his death.
His controversial step-father John Marshe Dickinson of Dunstable died in 1771. Smithson enrolled at Pembroke College, Oxford in 1782 and graduated in 1786 being promoted to MA; the poet George Keate was a first cousin once removed, on his mother's side. Smithson was nomadic in his lifestyle, travelling throughout Europe; as a student, in 1784, he participated in a geological expedition with Barthélemy Faujas de Saint-Fond, William Thornton and Paolo Andreani of Scotland and the Hebrides. He was in Paris during the French Revolution. In August 1807 Smithson became a prisoner of war while in Tönning during the Napoleonic Wars, he arranged a transfer to Hamburg. The following year, Smithson wrote to Sir Joseph Banks and asked him to use his influence to help free Smithson. Banks succeeded and Smithson returned to England, he never had children. Smithson's wealth stemmed from the splitting of his mother's estate with his half-brother, Col. Henry Louis Dickenson. Smithson's research work was eclectic, he studied subjects ranging from coffee making to the use of calamine renamed smithsonite, in making brass.
He studied the chemistry of human tears, snake venom and other natural occurrences. Smithson would publish twenty-seven papers, he was nominated to the Royal Society of London by Henry Cavendish and was made a fellow on 26 April 1787. Smithson socialised and worked with scientists Joseph Priestley, Sir Joseph Banks, Antoine Lavoisier, Richard Kirwan, his first paper was presented at the Royal Society on 7 July 1791, "An Account of Some Chemical Experiments on Tabasheer." Tabasheer is a substance used in traditional Indian medicine and derived from material collected inside bamboo culms. The samples that Macie analysed had been sent by physician-naturalist in India. In 1802 he read his second paper, "A Chemical Analysis of Some Calamines," at the Royal Society, it was published in the Philosophical Transactions of the Royal Society of London and was the documented instance of his new name, James Smithson. In the paper, Smithson challenges the idea, his discoveries made calamine a "true mineral." He examined Kirkdale Cave.
Smithson is credited with first using the word "silicates". Smithson's bank records at C. Hoare & Co show extensive and regular income derived from Apsley Pellatt, which suggests that Smithson had a strong financial or scientific relationship with the Blackfriars glass maker. Smithson died in Genoa, Italy on 27 June 1829, he was buried in Sampierdarena in a Protestant cemetery. In his will, Smithson left his fortune to the son of his half-brother – that is, his nephew, Henry James Dickenson. In the will, written in 1826, Smithson stated that Henry James Hungerford, or Hungerford's children, would receive his inheritance, that if his nephew did not live, had no children to receive the fortune, it would be donated to the United States to have an educational institution called the Smithsonian Institution founde
In mineralogy, crystal habit is the characteristic external shape of an individual crystal or crystal group. A single crystal's habit is a description of its general shape and its crystallographic forms, plus how well developed each form is. Recognizing the habit may help in identifying a mineral; when the faces are well-developed due to uncrowded growth a crystal is called euhedral, one with developed faces is subhedral, one with undeveloped crystal faces is called anhedral. The long axis of a euhedral quartz crystal has a six-sided prismatic habit with parallel opposite faces. Aggregates can be formed of individual crystals with euhedral to anhedral grains; the arrangement of crystals within the aggregate can be characteristic of certain minerals. For example, minerals used for asbestos insulation grow in a fibrous habit, a mass of fine fibers; the terms used by mineralogists to report crystal habits describe the typical appearance of an ideal mineral. Recognizing the habit can aid in identification as some habits are characteristic.
Most minerals, however, do not display ideal habits due to conditions during crystallization. Euhedral crystals formed in uncrowded conditions with no adjacent crystal grains are not common. Factors influencing habit include: a combination of two or more crystal forms. Minerals belonging to the same crystal system do not exhibit the same habit; some habits of a mineral are unique to its variety and locality: For example, while most sapphires form elongate barrel-shaped crystals, those found in Montana form stout tabular crystals. Ordinarily, the latter habit is seen only in ruby. Sapphire and ruby are both varieties of the same mineral: corundum; some minerals may replace other existing minerals while preserving the original's habit: this process is called pseudomorphous replacement. A classic example is tiger's eye quartz, crocidolite asbestos replaced by silica. While quartz forms prismatic crystals, in tiger's eye the original fibrous habit of crocidolite is preserved; the names of crystal habits are derived from: Predominant crystal faces.
Crystal forms. Aggregation of crystals or aggregates. Crystal appearance. Abnormal grain growth Grain growth
Transparency and translucency
In the field of optics, transparency is the physical property of allowing light to pass through the material without being scattered. On a macroscopic scale, the photons can be said to follow Snell's Law. Translucency is a superset of transparency: it allows light to pass through, but does not follow Snell's law. In other words, a translucent medium allows the transport of light while a transparent medium not only allows the transport of light but allows for image formation. Transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color; the opposite property of translucency is opacity. When light encounters a material, it can interact with it in several different ways; these interactions depend on the nature of the material. Photons interact with an object by some combination of reflection and transmission; some materials, such as plate glass and clean water, transmit much of the light that falls on them and reflect little of it.
Many liquids and aqueous solutions are transparent. Absence of structural defects and molecular structure of most liquids are responsible for excellent optical transmission. Materials which do not transmit light are called opaque. Many such substances have a chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of white light frequencies, they absorb certain portions of the visible spectrum while reflecting others. The frequencies of the spectrum which are not absorbed are either reflected or transmitted for our physical observation; this is. The attenuation of light of all frequencies and wavelengths is due to the combined mechanisms of absorption and scattering. Transparency can provide perfect camouflage for animals able to achieve it; this is easier in turbid seawater than in good illumination. Many marine animals such as jellyfish are transparent. With regard to the absorption of light, primary material considerations include: At the electronic level, absorption in the ultraviolet and visible portions of the spectrum depends on whether the electron orbitals are spaced such that they can absorb a quantum of light of a specific frequency, does not violate selection rules.
For example, in most glasses, electrons have no available energy levels above them in range of that associated with visible light, or if they do, they violate selection rules, meaning there is no appreciable absorption in pure glasses, making them ideal transparent materials for windows in buildings. At the atomic or molecular level, physical absorption in the infrared portion of the spectrum depends on the frequencies of atomic or molecular vibrations or chemical bonds, on selection rules. Nitrogen and oxygen are not greenhouse gases because there is no absorption, but because there is no molecular dipole moment. With regard to the scattering of light, the most critical factor is the length scale of any or all of these structural features relative to the wavelength of the light being scattered. Primary material considerations include: Crystalline structure: whether or not the atoms or molecules exhibit the'long-range order' evidenced in crystalline solids. Glassy structure: scattering centers include fluctuations in density or composition.
Microstructure: scattering centers include internal surfaces such as grain boundaries, crystallographic defects and microscopic pores. Organic materials: scattering centers include fiber and cell structures and boundaries. Diffuse reflection - Generally, when light strikes the surface of a solid material, it bounces off in all directions due to multiple reflections by the microscopic irregularities inside the material, by its surface, if it is rough. Diffuse reflection is characterized by omni-directional reflection angles. Most of the objects visible to the naked eye are identified via diffuse reflection. Another term used for this type of reflection is "light scattering". Light scattering from the surfaces of objects is our primary mechanism of physical observation. Light scattering in liquids and solids depends on the wavelength of the light being scattered. Limits to spatial scales of visibility therefore arise, depending on the frequency of the light wave and the physical dimension of the scattering center.
Visible light has a wavelength scale on the order of a half a micrometer. Scattering centers as small. Optical transparency in polycrystalline materials is limited by the amount of light, scattered by their microstructural features. Light scattering depends on the wavelength of the light. Limits to spatial scales of visibility therefore arise, depending on the frequency of the light wave and the physical dimension of the scattering center. For example, since visible light has a wavelength scale on the order of a micrometer, scattering centers will have dimensions on a similar spatial scale. Primary scattering centers in polycrystalline materi
Anglesite is a lead sulfate mineral with the chemical formula PbSO4. It occurs as an oxidation product of galena. Anglesite occurs as prismatic orthorhombic crystals and earthy masses, is isomorphous with barite and celestine, it contains 74% of lead by mass and therefore has a high specific gravity of 6.3. Anglesite's color is gray with pale yellow streaks, it may be dark gray if impure. It was first recognized as a mineral species by William Withering in 1783, who discovered it in the Parys copper-mine in Anglesey; the crystals from Anglesey, which were found abundantly on a matrix of dull limonite, are small in size and simple in form, being bounded by four faces of a prism and four faces of a dome. Crystals from some other localities, notably from Monteponi in Sardinia, are transparent and colourless, possessed of a brilliant adamantine lustre, modified by numerous bright faces; the variety of combinations and habits presented by the crystals is extensive, nearly two hundred distinct forms being figured by V. von Lang in his monograph of the species.
There are distinct cleavages parallel to the faces of the prism and the basal plane, but these are not so well developed as in the isomorphous minerals barite and celestite. Anglesite is a mineral of secondary origin, having been formed by the oxidation of galena in the upper parts of mineral lodes where these have been affected by weathering processes. At Monteponi the crystals encrust cavities in glistening granular galena. At most localities it is found as isolated crystals in the lead-bearing lodes, but at some places, in Australia and Mexico, it occurs as large masses, is mined as an ore of lead. Anglesite is sometimes used as a gemstone. Lead sulfate