Quartz is the second most abundant mineral in Earths continental crust, behind feldspar. 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. The word quartz is derived from the German word Quarz and its Middle High German ancestor twarc, the Ancient Greeks referred to quartz as κρύσταλλος derived from the Ancient Greek κρύος meaning icy cold, because some philosophers apparently believed the mineral to be a form of supercooled ice. Today, the rock crystal is sometimes used as an alternative name for the purest form of quartz. Quartz belongs to the crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end, 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, 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 crystal system, space group P3121 and P3221 respectively. β-quartz belongs to the system, space group P6222 and P6422. These space groups are truly chiral, both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks. The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, 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 an identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, common colored varieties include citrine, rose quartz, smoky quartz, milky quartz, and others.
The most important distinction between types of quartz is that of macrocrystalline and the microcrystalline or cryptocrystalline varieties, the cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a 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, heliotrope, amethyst is a form of quartz that ranges from a bright to dark or dull purple color. The worlds largest deposits of amethysts can be found in Brazil, Uruguay, France, sometimes amethyst and citrine are found growing in the same crystal. It is referred to as ametrine, an amethyst is formed when there is iron in the area where it was formed
A pegmatite is a holocrystalline, intrusive igneous rock composed of interlocking phaneritic crystals usually larger than 2.5 cm in size, such rocks are referred to as pegmatitic. The word pegmatite derives from Homeric Greek, πεγνυμι, which means “to bind together”, in reference to the crystals of quartz. Most pegmatites are composed of quartz and mica, having a similar composition as granite. Crystal size is the most striking feature of pegmatites, with usually over 5 cm in size. Individual crystals over 10 metres long have been found, and many of the worlds largest crystals were found within pegmatites and these include, microcline and tourmaline. Similarly, crystal texture and form within pegmatitic rock may be taken to extreme size, perthite feldspar within a pegmatite often shows gigantic perthitic texture visible to the naked eye. The single feature that is diagnostic to all pegmatites is their large size crystal components, Pegmatite bodies are usually of minor size compared to typical intrusive rock bodies.
Pegmatite body size is on the order of magnitude of one to a few hundred meters, compared to typical igneous rocks they are rather inhomogeneous and may show zones with different mineral assemblages. Crystal size and mineral assemblages are usually oriented parallel to the rock or even concentric for pegmatite lenses. Crystal growth rates in pegmatite must be slow to allow gigantic crystals to grow within the confines and pressures of the Earths crust. The mineralogy of a pegmatite is in most cases dominated by some form of feldspar, often with mica and usually with quartz and this is because of the difficulty in counting and sampling mineral grains in a rock which may have crystals from centimeters to meters across. Garnet, commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic, pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red and brown almandine garnet. Syenite pegmatites are quartz depleted and contain large feldspathoid crystals instead, Pegmatite is difficult to sample representatively due to the large size of the constituent mineral crystals.
Often, bulk samples of some 50–60 kg of rock must be crushed to obtain a meaningful, pegmatite is often characterised by sampling the individual minerals which comprise the pegmatite, and comparisons are made according to mineral chemistry. Occasionally, enrichment in the trace elements will result in crystallisation of equally unusual and rare minerals such as beryl, columbite, zinnwaldite. Pegmatites are the source of lithium either as spodumene, lithiophyllite or usually from lepidolite. The primary source for caesium is pollucite, a mineral from a zoned pegmatite, the majority of the worlds beryllium is sourced from non-gem quality beryl within pegmatite. Tantalum, rare-earth elements are sourced from a few pegmatites worldwide, bismuth and tin have been won from pegmatite, but this is not yet an important source of these metals
The mountain range forms part of the conventional boundary between the continents of Europe and Asia. Vaygach Island and the islands of Novaya Zemlya form a continuation of the chain to the north into the Arctic Ocean. The mountains lie within the Ural geographical region and significantly overlap with the Ural Federal District and they have rich resources, including metal ores, coal and semi-precious stones. Since the 18th century the mountains have contributed significantly to the sector of the Russian economy. As attested by Sigismund von Herberstein, in the 16th century Russians called the range by a variety of names derived from the Russian words for rock and it might have been a borrowing from either Turkic stone belt, or Ob-Ugric. From the 13th century, in Bashkortostan there has been a legend about a hero named Ural and he sacrificed his life for the sake of his people and they poured a stone pile over his grave, which turned into the Ural Mountains. Possibilities include Bashkir үр elevation, upland or Mansi ур ала mountain peak, top of the mountain, tatischev believes that this oronym is set to belt and associates it with the Turkic verb oralu- gird.
Dobrodomov suggests a transition from Aral to Ural explained on the basis of ancient Bulgar-Chuvash dialects, hawks believes that the name goes back to the Bashkir folklore Ural-Batyr. Shumilov suggested a Mongolian origin, Khural Uul, that is, the Evenk geographical term era mountain has been theorized. Finno-Ugrist scholars consider Ural deriving from the Mansi word urr meaning a mountain, turkologists, on the other hand, have achieved majority support for their assertion that ural in Tatar means a belt, and recall that an earlier name for the range was stone belt. During the next few centuries Novgorodians engaged in fur trading with the population and collected tribute from Yugra and Great Perm. The rivers Chusovaya and Belaya were first mentioned in the chronicles of 1396 and 1468, in 1430 the town of Solikamsk was founded on the Kama at the foothills of the Ural, where salt was produced in open pans. Ivan III of Moscow captured Perm and Yugra from the declining Novgorod Republic in 1472, with the excursions of 1483 and 1499–1500 across the Ural Moscow managed to subjugate Yugra completely.
The Middle and Southern Ural were still largely unavailable and unknown to the Russian or Western European geographers, the Stroganovs land provided the staging ground for Yermaks incursion into Siberia. Yermak crossed the Ural from the Chusovaya to the Tagil around 1581, in 1597 Babinovs road was built across the Ural from Solikamsk to the valley of the Tura, where the town of Verkhoturye was founded in 1598. Customs was established in Verkhoturye shortly thereafter and the road was made the legal connection between European Russia and Siberia for a long time. In 1648 the town of Kungur was founded at the foothills of the Middle Ural. During the 17th century the first deposits of iron and copper ores, gemstones and copper smelting works emerged
Conchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation. Materials that break in this way include quartz, quartzite and other fine-grained or amorphous materials with a composition of pure silica, such as obsidian, conchoidal fractures can occur in other materials under favorable circumstances. This material property was used in the Stone Age to make sharp tools. Conchoidal fractures often result in a curved surface that resembles the rippling, gradual curves of a mussel shell. A swelling appears at the point of impact called the bulb of percussion, shock waves emanating outwards from this point leave their mark on the stone as ripples. Other conchoidal features include small fissures emanating from the bulb of percussion and this property makes such fractures useful in engineering, since they provide a permanent record of the stress state at the time of failure. As conchoidal fractures can be produced only by mechanical impact, rather than frost cracking for example, the dictionary definition of conchoid at Wiktionary
Afghanistan, officially the Islamic Republic of Afghanistan, is a landlocked country located within South Asia and Central Asia. It has a population of approximately 32 million, making it the 42nd most populous country in the world. It is bordered by Pakistan in the south and east, Iran in the west, Turkmenistan and Tajikistan in the north and its territory covers 652,000 km2, making it the 41st largest country in the world. The land served as the source from which the Kushans, Samanids, Ghaznavids, Khiljis, Hotaks, the political history of the modern state of Afghanistan began with the Hotak and Durrani dynasties in the 18th century. In the late 19th century, Afghanistan became a state in the Great Game between British India and the Russian Empire. Following the Third Anglo-Afghan War in 1919, King Amanullah unsuccessfully attempted to modernize the country and it remained peaceful during Zahir Shahs forty years of monarchy. A series of coups in the 1970s was followed by a series of wars that devastated much of Afghanistan.
The name Afghānistān is believed to be as old as the ethnonym Afghan, the root name Afghan was used historically in reference to a member of the ethnic Pashtuns, and the suffix -stan means place of in Persian. Therefore, Afghanistan translates to land of the Afghans or, more specifically in a historical sense, the modern Constitution of Afghanistan states that he word Afghan shall apply to every citizen of Afghanistan. An important site of historical activities, many believe that Afghanistan compares to Egypt in terms of the historical value of its archaeological sites. The country sits at a unique nexus point where numerous civilizations have interacted and it has been home to various peoples through the ages, among them the ancient Iranian peoples who established the dominant role of Indo-Iranian languages in the region. At multiple points, the land has been incorporated within large regional empires, among them the Achaemenid Empire, the Macedonian Empire, the Indian Maurya Empire, and the Islamic Empire.
Archaeological exploration done in the 20th century suggests that the area of Afghanistan has been closely connected by culture and trade with its neighbors to the east, west. Artifacts typical of the Paleolithic, Neolithic, urban civilization is believed to have begun as early as 3000 BCE, and the early city of Mundigak may have been a colony of the nearby Indus Valley Civilization. More recent findings established that the Indus Valley Civilisation stretched up towards modern-day Afghanistan, making the ancient civilisation today part of Pakistan, Afghanistan, in more detail, it extended from what today is northwest Pakistan to northwest India and northeast Afghanistan. An Indus Valley site has found on the Oxus River at Shortugai in northern Afghanistan. There are several smaller IVC colonies to be found in Afghanistan as well, after 2000 BCE, successive waves of semi-nomadic people from Central Asia began moving south into Afghanistan, among them were many Indo-European-speaking Indo-Iranians.
These tribes migrated further into South Asia, Western Asia, the region at the time was referred to as Ariana
Fluorite is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals and it crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. Mohs scale of hardness, based on scratch Hardness comparison. Fluorite is a mineral, both in visible and ultraviolet light, and the stone has ornamental and lapidary uses. Industrially, fluorite is used as a flux for smelting, and in the production of certain glasses, the purest grades of fluorite are a source of fluoride for hydrofluoric acid manufacture, which is the intermediate source of most fluorine-containing fine chemicals. Optically clear transparent fluorite lenses have low dispersion, so made from it exhibit less chromatic aberration. Fluorite optics are usable in the range, where conventional glasses are too absorbent for use. The word fluorite is derived from the Latin verb fluere, meaning to flow, the mineral is used as a flux in iron smelting to decrease the viscosity of slags.
The term flux comes from the Latin adjective fluxus, meaning flowing, agricola, a German scientist with expertise in philology and metallurgy, named fluorspar as a neo-Latinization of the German Flussspat from Fluß and Spat. In 1852, fluorite gave its name to the phenomenon of fluorescence, Fluorite gave the name to its constitutive element fluorine. Presently, the fluorspar is most commonly used for fluorite as the industrial and chemical commodity, while fluorite is used mineralogically. Fluorite crystallises in a cubic motif, crystal twinning is common and adds complexity to the observed crystal habits. Fluorite has four perfect cleavage planes that help produce octahedral fragments, element substitution for the calcium cation often includes certain rare earth elements, such as yttrium and cerium. Iron and barium are common impurities, some fluorine may be replaced by the chloride anion. Fluorite is a widely occurring mineral that occurs globally with significant deposits in over 9,000 areas.
It may occur as a deposit, especially with metallic minerals, where it often forms a part of the gangue and may be associated with galena, barite, quartz. It is a mineral in deposits of hydrothermal origin and has been noted as a primary mineral in granites and other igneous rocks. The world reserves of fluorite are estimated at 230 million tonnes with the largest deposits being in South Africa, China is leading the world production with about 3 Mt annually, followed by Mexico, Russia, South Africa and Namibia
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, Fluorescence occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and it was derived from the wood of two tree species, Pterocarpus indicus and Eysenhardtia polystachya. The chemical compound responsible for this fluorescence is matlaline, which is the product of one of the flavonoids found in this wood. The name was derived from the fluorite, some examples of which contain traces of divalent europium. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight, the specific frequencies of exciting and emitted light are dependent on the particular system. S0 is called the state of the fluorophore, and S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways and it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent.
Excited organic molecules can relax via conversion to a triplet state, relaxation from S1 can occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an extremely efficient quencher of fluorescence just because of its unusual triplet ground state, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation, this phenomenon is known as the Stokes shift. The emitted radiation may be of the wavelength as the absorbed radiation. Molecules that are excited through light absorption or via a different process can transfer energy to a second sensitized molecule, the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed, Φ = Number of photons emitted Number of photons absorbed The maximum fluorescence quantum yield is 1.0, each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent, thus, if the rate of any pathway changes, both the excited state lifetime and the fluorescence quantum yield will be affected.
Fluorescence quantum yields are measured by comparison to a standard, the quinine salt quinine sulfate in a sulfuric acid solution is a common fluorescence standard. The fluorescence lifetime refers to the time the molecule stays in its excited state before emitting a photon. This is an instance of exponential decay, various radiative and non-radiative processes can de-populate the excited state
Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning light, a range of terms are used to describe lustre, such as earthy, metallic and silky. Similarly, the term refers to a glassy lustre. A list of terms is given below. Lustre varies over a continuum, and so there are no rigid boundaries between the different types of lustre. The terms are frequently combined to describe types of lustre. Some minerals exhibit unusual optical phenomena, such as asterism or chatoyancy, a list of such phenomena is given below. Adamantine minerals possess a superlative lustre, which is most notably seen in diamond, such minerals are transparent or translucent, and have a high refractive index. Minerals with an adamantine lustre are uncommon, with examples being cerussite. Minerals with a degree of lustre are referred to as subadamantine, with some examples being garnet. Dull minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, a distinction is sometimes drawn between dull minerals and earthy minerals, with the latter being coarser, and having even less lustre.
Greasy minerals resemble fat or grease, a greasy lustre often occurs in minerals containing a great abundance of microscopic inclusions, with examples including opal and cordierite. Many minerals with a greasy lustre feel greasy to the touch, metallic minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface. Examples include galena and magnetite, pearly minerals consist of thin transparent co-planar sheets. Light reflecting from these layers give them a lustre reminiscent of pearls, such minerals possess perfect cleavage, with examples including muscovite and stilbite. Resinous minerals have the appearance of resin, chewing gum or plastic, a principal example is amber, which is a form of fossilized resin. Silky minerals have an arrangement of extremely fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos and the satin spar variety of gypsum, a fibrous lustre is similar, but has a coarser texture
Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals and its luster and multiple crystal faces produce a desirable gem. Cassiterite has been the chief tin ore throughout ancient history and remains the most important source of tin today, most sources of cassiterite today are found in alluvial or placer deposits containing the resistant weathered grains. The best sources of primary cassiterite are found in the tin mines of Bolivia, rwanda has a nascent cassiterite mining industry. Fighting over cassiterite deposits is a cause of the conflict waged in eastern parts of the Democratic Republic of the Congo. This has led to cassiterite being considered a conflict mineral, cassiterite is a widespread minor constituent of igneous rocks. The Bolivian veins and the old exhausted workings of Cornwall, are concentrated in high temperature quartz veins, the veins commonly contain tourmaline, fluorite, wolframite and arsenopyrite. The mineral occurs extensively in Cornwall as surface deposits on Bodmin Moor, for example, the current major tin production comes from placer or alluvial deposits in Malaysia, Indonesia, the Maakhir region of Somalia, and Russia.
Hydraulic mining methods are used to concentrate mined ore, a process which relies on the specific gravity of the SnO2 ore. Crystal twinning is common in cassiterite and most aggregate specimens show crystal twins, the typical twin is bent at a near-60-degree angle, forming an elbow twin. Botryoidal or reniform cassiterite is called wood tin, cassiterite is used as a gemstone and collector specimens when quality crystals are found
Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a metallic luster. It is a member of group 14 in the table, along with carbon above it and germanium, lead. It is not very reactive, although more reactive than germanium, Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earths crust. It is most widely distributed in dusts, planetoids, over 90% of the Earths crust is composed of silicate minerals, making silicon the second most abundant element in the Earths crust after oxygen. Most silicon is used commercially without being separated, and often with little processing of the natural minerals, such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with sand and gravel to make concrete for walkways, foundations. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass, Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics.
Elemental silicon has an impact on the modern world economy. Most free silicon is used in the refining, aluminium-casting. Silicon is the basis of the widely used synthetic polymers called silicones, Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa and many grasses. Silicon is a solid at room temperature, with a point of 1,414 °C. Like water, it has a density in a liquid state than in a solid state and it expands when it freezes. With a relatively high conductivity of 149 W·m−1·K−1, silicon conducts heat well. In its crystalline form, pure silicon has a gray color, like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a cubic crystal structure with a lattice spacing of 0.5430710 nm.
The outer electron orbital of silicon, like that of carbon, has four valence electrons, the 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six
The gemstone irradiation is a process in which a gemstone is artificially irradiated in order to enhance its optical properties. High levels of ionizing radiation can change the structure of the gemstones crystal lattice. As a result, the color may be significantly altered or the visibility of its inclusions may be lessened. Irradiation has enabled the creation of gemstone colors that do not exist or are rare in nature. Certain natural gemstone colors, such as colors in diamonds, are the results of the exposure to natural radiation in the earth. The limited penetrating ability of these result in partial coloring of the diamonds surface. Irradiation, particularly when done in a reactor, can make gemstones slightly radioactive. The first documented artificially irradiated gemstone was created by English chemist Sir William Crookes in 1905, after having been kept there for 16 months, the previously colorless diamond became green. This method produced a high degree of long-term residual radioactivity and is no longer in use.
However, radium-treated green diamonds are still found in markets. The concerns for health risks related to the residual radioactivity of the gemstones led to government regulations in many countries. In the United States, the Nuclear Regulatory Commission has set limits on the allowable levels of residual radioactivity before an irradiated gemstone can be distributed in the country. All neutron- or electron beam-irradiated gemstones must be tested by an NRC-licensee prior to release for sales, in India, the Bhabha Atomic Research Centre started irradiating gemstones in the early 1970s. In Thailand, the Office of Atoms for Peace conducts the process for private sectors, the most commonly irradiated gemstone is topaz, which becomes blue after the process. Blue topaz is very rare in nature and almost always the result of artificial irradiation, according to the American Gem Trade Association, approximately 30 million carats of topaz are irradiated every year globally,40 percent of which were done in the United States as of 1988.
As of 2011, no topaz is neutron irradiated in the US, major treatment areas are Germany, a lot of linear accelerated treatment is done in Bangkok. Diamonds are usually irradiated to become yellow, blue-green or green, quartz may be irradiated to produce amethyst and other colors. Colorless beryls, called goshenite, become pure yellow when irradiated, pearls are irradiated to produce gray blue or gray-to-black colors
Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays.
Under some conditions and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established.
The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann