Beryl is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include aquamarine. Occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are rare. Pure beryl is colorless, but it is tinted by impurities. Beryl is an ore source of beryllium; the name "beryl" is derived from Greek βήρυλλος beryllos which referred to a "precious blue-green color-of-sea-water stone". The term was adopted for the mineral beryl more exclusively; when the first eyeglasses were constructed in 13th century Italy, the lenses were made of beryl as glass could not be made clear enough. Glasses were named Brillen in German. Beryl of various colors is found most in granitic pegmatites, but occurs in mica schists in the Ural Mountains, limestone in Colombia. Beryl is associated with tin and tungsten ore bodies. Beryl is found in Europe in Norway, Germany, Sweden and Russia, as well as Brazil, Madagascar, Pakistan, South Africa, the United States, Zambia.
US beryl locations are in California, Connecticut, Idaho, New Hampshire, North Carolina, South Dakota and Utah. New England's pegmatites have produced some of the largest beryls found, including one massive crystal from the Bumpus Quarry in Albany, Maine with dimensions 5.5 by 1.2 m with a mass of around 18 metric tons. As of 1999, the world's largest known occurring crystal of any mineral is a crystal of beryl from Malakialina, Madagascar, 18 m long and 3.5 m in diameter, weighing 380,000 kg. Beryl belongs to the hexagonal crystal system. Beryl forms hexagonal columns but can occur in massive habits; as a cyclosilicate beryl incorporates rings of silicate tetrahedra of Si 6 O 18 that are arranged in columns along the C axis and as parallel layers perpendicular to the C axis, forming channels along the C axis. These channels permit a variety of ions, neutral atoms, molecules to be incorporated into the crystal thus disrupting the overall charge of the crystal permitting further substitutions in Aluminium and Beryllium sites in the crystal structure.
These impurities give rise to the variety of colors of beryl. Increasing alkali content within the silicate ring channels causes increases to the refractive indices and birefringence. Aquamarine is a cyan variety of beryl, it occurs at most localities. The gem-gravel placer deposits of Sri Lanka contain aquamarine. Green-yellow beryl, such as that occurring in Brazil, is sometimes called chrysolite aquamarine; the deep blue version of aquamarine is called maxixe. Maxixe is found in the country of Madagascar, its color fades to white when exposed to sunlight or is subjected to heat treatment, though the color returns with irradiation. The pale blue color of aquamarine is attributed to Fe2+. Fe3+ ions produce golden-yellow color, when both Fe2+ and Fe3+ are present, the color is a darker blue as in maxixe. Decoloration of maxixe by light or heat thus may be due to the charge transfer between Fe3+ and Fe2+. Dark-blue maxixe color can be produced in green, pink or yellow beryl by irradiating it with high-energy particles.
In the United States, aquamarines can be found at the summit of Mt. Antero in the Sawatch Range in central Colorado. In Wyoming, aquamarine has been discovered near Powder River Pass. Another location within the United States is the Sawtooth Range near Stanley, although the minerals are within a wilderness area which prevents collecting. In Brazil, there are mines in the states of Minas Gerais, Espírito Santo, Bahia, minorly in Rio Grande do Norte; the mines of Colombia, Madagascar, Malawi and Kenya produce aquamarine. The largest aquamarine of gemstone quality mined was found in Marambaia, Minas Gerais, Brazil, in 1910, it weighed over 110 kg, its dimensions were 48.5 cm long and 42 cm in diameter. The largest cut aquamarine gem is the Dom Pedro aquamarine, now housed in the Smithsonian Institution's National Museum of Natural History; the ancient Romans believed that aquamarine would protect against any dangers while travelling at sea, that it provided energy and cured laziness. Emerald is green beryl, sometimes vanadium.
Most emeralds are included, so their brittleness is classified as poor. The modern English word "emerald" comes via Middle English Emeraude, imported from modern French via Old French Ésmeraude and Medieval Latin Esmaraldus, from Latin smaragdus, from Greek σμάραγδος smaragdos meaning ‘green gem’, from Hebrew ברקת bareket, meaning ‘lightning flash’, referring to ‘emerald’, relating to Akkadian baraqtu, meaning ‘emerald’, relating to the Sanskrit word मरकत marakata, meaning ‘green’; the Semitic word אזמרגד izmargad, meaning ` emerald', is a back-loan. Emeralds in antiquity were mined by the Egyptians and in what is now Austria, as well as Swat in contemporary Pakistan. A ra
Tiger's eye is a chatoyant gemstone, a metamorphic rock with a golden to red-brown colour and a silky lustre. As members of the quartz group, tiger's eye and the related blue-coloured mineral hawk's eye gain their silky, lustrous appearance from the parallel intergrowth of quartz crystals and altered amphibole fibres that have turned into limonite. Tiger iron is an altered rock composed chiefly of red jasper and black hematite; the undulating, contrasting bands of colour and lustre make for an attractive motif and it is used for jewellery-making and ornamentation. Tiger iron is a popular ornamental material used in a variety of applications, from beads to knife hilts. Tiger iron is mined in South Africa and Western Australia. Tiger's eye is composed chiefly of silicon dioxide and is coloured by iron oxide; the specific gravity ranges from 2.64 to 2.71. It is formed by the alteration of crocidolite. Serpentine deposits in which are found chatoyant bands of chrysotile fibres have been found in the US states of Arizona and California.
These have been sold as "Arizona tiger-eye" and "California tiger's eye" gemstones. The trade name of pietersite is used for a fractured or brecciated chalcedony containing amphibole fibers and promoted as tiger's eye from Namibia and China. Common sources of tiger's eye include Australia, India, South Africa, the United States, Canada, China and Spain. In some parts of the world, the stone is believed to ward off the evil eye. Gems are given a cabochon cut to best display their chatoyance. Red stones are developed by gentle heat treatments. Dark stones are artificially lightened to improve colour using a nitric acid treatment. Honey-coloured stones have been used to imitate the more valued cat's eye chrysoberyl, but the overall effect is unconvincing. Artificial fibre optic glass is a common imitation of tiger's eye, is produced in a wide range of colours. New interpretation of the origin of tiger's-eye: Comment and Reply
Charoite is a rare silicate mineral, first described in 1978 and named for the Chara River. It has been reported only from the Sakha Republic, Russia, it is found where a syenite of the Murunskii Massif has intruded into and altered limestone deposits producing a potassium feldspar metasomatite. Charoite is translucent lavender to purple in color with a pearly luster. Charoite is massive in nature, fractures are conchoidal, it has an unusual swirling, fibrous appearance, sometimes chatoyant, that, along with its intense color, can lead many to believe at first that it is synthetic or enhanced artificially. Though discovered in the 1940s, it was not known to most of the world until its description in 1978, it is said to be unattractive when found in the field. Charoite occurs in association with tinaksite and canasite
Titanium dioxide known as titanium oxide or titania, is the occurring oxide of titanium, chemical formula TiO2. When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891, it is sourced from ilmenite and anatase. It has a wide range of applications, including paint and food coloring; when used as a food coloring, it has E number E171. World production in 2014 exceeded 9 million metric tons, it has been estimated that titanium dioxide is used in two-thirds of all pigments, pigments based on the oxide has been valued at $13.2 billion. Titanium dioxide occurs in nature as the well-known minerals rutile and brookite, additionally as two high pressure forms, a monoclinic baddeleyite-like form and an orthorhombic α-PbO2-like form, both found at the Ries crater in Bavaria. One of these is known as akaogiite is an rare mineral, it is sourced from ilmenite ore. This is the most widespread form of titanium dioxide-bearing ore around the world. Rutile is the next contains around 98 % titanium dioxide in the ore.
The metastable anatase and brookite phases convert irreversibly to the equilibrium rutile phase upon heating above temperatures in the range 600–800 °C. Titanium dioxide has eight modifications – in addition to rutile and brookite, three metastable phases can be produced synthetically, five high-pressure forms exist: The cotunnite-type phase was claimed by L. Dubrovinsky and co-authors to be the hardest known oxide with the Vickers hardness of 38 GPa and the bulk modulus of 431 GPa at atmospheric pressure; however studies came to different conclusions with much lower values for both the hardness and bulk modulus. The oxides are commercially important ores of titanium; the metal can be mined from other minerals such as ilmenite or leucoxene ores, or one of the purest forms, rutile beach sand. Star sapphires and rubies get their asterism from rutile impurities present in them. Titanium dioxide is found as a mineral in magmatic rocks and hydrothermal veins, as well as weathering rims on perovskite.
TiO2 forms lamellae in other minerals. Molten titanium dioxide has a local structure in which each Ti is coordinated to, on average, about 5 oxygen atoms; this is distinct from the crystalline forms. Spectral lines from titanium oxide are prominent in class M stars, which are cool enough to allow molecules of this chemical to form; the production method depends on the feedstock. The most common mineral source is ilmenite; the abundant Rutile mineral sand can be purified with the chloride process or other processes. Ilmenite is converted into pigment grade titanium dioxide via either the sulfate process or the chloride process. Both Sulfate and Chloride Processes produce the titanium dioxide pigment in the rutile crystal form, but the Sulfate Process can be adjusted to produce the anatase form. Anatase, being softer, is used in paper applications; the Sulfate Process is run as a batch process. Plants using the Sulfate Process require ilmenite concentrate or pretreated feedstocks as suitable source of titanium.
In the sulfate process Ilmenite is treated with sulfuric acid to extract iron sulfate pentahydrate. The resulting synthetic rutile is further processed according to the specifications of the end user, i.e. pigment grade or otherwise. In another method for the production of synthetic rutile from ilmenite the Becher Process first oxidizes the ilmenite as a means to separate the iron component. An alternative process, known as the Chloride process converts ilmenite or other titanium sources to Titanium tetrachloride via reaction with elemental chlorine, purified by distillation, reacted with oxygen to regenerate chlorine and produce the Titanium dioxide. Titanium dioxide pigment can be produced from higher titanium content feedstocks such as upgraded slag and leucoxene via a chloride acid process; the five largest TiO2 pigment processors are in 2019 Chemours, Cristal Global, Venator-Huntsman and Tronox, the largest one. Major paint and coating company end users for pigment grade titanium dioxide include Akzo Nobel, PPG Industries, Sherwin Williams, BASF, Kansai Paints and Valspar.
Global TiO2 pigment demand for 2010 was 5.3 Mt with annual growth expected to be about 3-4%. For specialty applications, TiO2 films are prepared by various specialized chemistries. Sol-gel routes involve the hydrolysis of titanium alkoxides, such as titanium ethoxide: Ti4 + 2 H2O → TiO2 + 4 EtOHThis technology is suited for the preparation of films. A related approach that relies on molecular precursors involves chemical vapor deposition. In this application, the alkoxide is volatilized and decomposed on contact with a hot surface: Ti4 → TiO2 + 2 Et2O The most important application areas are paints and varnishes as well as paper and plastics, which account for about 80% of the world's titanium dioxide consumption. Other pigment applications such as printing inks, rubber, cosmetic products and food account for another 8%; the rest is used in other applications, for instance the production of technical pure titanium and glass ceramics, electrical ceramics, metal patinas, electric conductors and chemical intermediates.
Titanium dioxide is the most used white pigment because of its brightness and high refractive index, in whi
A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks and organic materials that are not minerals are used for jewelry and are therefore considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity is another characteristic. Apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem maker is called a gemcutter; the traditional classification in the West, which goes back to the ancient Greeks, begins with a distinction between precious and semi-precious. In modern use the precious stones are diamond, ruby and emerald, with all other gemstones being semi-precious; this distinction reflects the rarity of the respective stones in ancient times, as well as their quality: all are translucent with fine color in their purest forms, except for the colorless diamond, hard, with hardnesses of 8 to 10 on the Mohs scale.
Other stones are classified by their color and hardness. The traditional distinction does not reflect modern values, for example, while garnets are inexpensive, a green garnet called tsavorite can be far more valuable than a mid-quality emerald. Another unscientific term for semi-precious gemstones used in art history and archaeology is hardstone. Use of the terms'precious' and'semi-precious' in a commercial context is, misleading in that it deceptively implies certain stones are intrinsically more valuable than others, not the case. In modern times gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology; the first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon and rubies of aluminium oxide. Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is found in.
For example, which have a cubic crystal system, are found as octahedrons. Gemstones are classified into different groups and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the emerald, red beryl, goshenite and morganite, which are all varieties of the mineral species beryl. Gems are characterized in terms of refractive index, specific gravity, cleavage and luster, they may exhibit double refraction. They may have a distinctive absorption spectrum. Material or flaws within a stone may be present as inclusions. Gemstones may be classified in terms of their "water"; this is a recognized grading of the gem's luster, transparency, or "brilliance". Transparent gems are considered "first water", while "second" or "third water" gems are those of a lesser transparency. There is no universally accepted grading system for gemstones. Diamonds are graded using a system developed by the Gemological Institute of America in the early 1950s.
All gemstones were graded using the naked eye. The GIA system included a major innovation: the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye. A mnemonic device, the "four Cs", has been introduced to help the consumer understand the factors used to grade a diamond. With modification, these categories can be useful in understanding the grading of all gemstones; the four criteria carry different weight depending upon whether they are applied to colored gemstones or to colorless diamonds. In diamonds, cut is the primary determinant of value, followed by color. Diamonds are meant to sparkle, to break down light into its constituent rainbow colors, chop it up into bright little pieces, deliver it to the eye. In its rough crystalline form, a diamond will do none of these things. In gemstones that have color, including colored diamonds, it is the purity and beauty of that color, the primary determinant of quality. Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent, unusual optical phenomena within the stone such as color zoning and asteria.
The Greeks, for example valued asteria gemstones, which were regarded as powerful love charms, Helen of Troy was known to have worn star-corundum. Aside from the diamond, the ruby, emerald and opal have been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone as well, going back to ancient Greece. In the last century certain stones such as aquamarine and cat's eye have been popular and hence been regarded as precious. Today such a distinction is no longer made by the gemstone trade. Many gemstones are used in the most expensive jewelr
Thomsonite is the name of a series of tecto-silicate minerals of the zeolite group. Prior to 1997, thomsonite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named thomsonite-Ca and thomsonite-Sr. Thomsonite-Ca, by far the more common of the two is a hydrous sodium and aluminium silicate, NaCa2Al5Si5O20·6H2O. Strontium can substitute for the calcium and the appropriate species name depends on the dominant element; the species are visually indistinguishable and the series name thomsonite is used whenever testing has not been performed. Globally, thomsonite is one of the rarer zeolites. Thomsonite was first identified in material from Scotland in 1820, it is named for the Scottish chemist Thomas Thomson. The crystal system of thomsonite is orthorhombic; the Mohs hardness is 5 to 5.5. It is transparent to translucent and has a density of 2.3 to 2.4. It may be colorless, beige, or somewhat green, yellow, or red.
The crystals tend to be long thin blades that form radial aggregates, sometimes fans and tufts. The aggregates are variable and may be spikey in appearance and ball-like, or form worm-like growths. Tight acicular radiating clusters and sphericules are common forms. Thomsonite occurs with other zeolites in the amygdaloidal cavities of basaltic volcanic rocks, in granitic pegmatites. Examples have been found in Faroe Islands, Arkansas, Michigan, New Jersey, Ontario, Nova Scotia and Russia. Nodules of massive thomsonite that display an attractive banded coloring are found along the shore of Lake Superior. Most of these thomsonite nodules and their derived pebbles are less than 0.6 cm. Those enclosed in basalt are difficult to remove without breaking them. A large percentage of those used as gemstones are from pebbles collected from beaches. Mindat Thomsonite-Ca Webmineral Thomsonite-Ca IMA Zeolite Classification R. V. Dietrich, Thomsonite Structure type THO
Epoxy is either any of the basic components or the cured end products of epoxy resins, as well as a colloquial name for the epoxide functional group. Epoxy resins known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. Epoxy resins may be reacted either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, phenols and thiols; these co-reactants are referred to as hardeners or curatives, the cross-linking reaction is referred to as curing. Reaction of polyepoxides with themselves or with polyfunctional hardeners forms a thermosetting polymer with favorable mechanical properties and high thermal and chemical resistance. Epoxy has a wide range of applications, including metal coatings, use in electronics/electrical components/LEDs, high tension electrical insulators, paint brush manufacturing, fiber-reinforced plastic materials and structural adhesives. Epoxy is sometimes used as a glue.
Epoxy resins are low molecular weight pre-polymers or higher molecular weight polymers which contain at least two epoxide groups. The epoxide group is sometimes referred to as a glycidyl or oxirane group. A wide range of epoxy resins are produced industrially; the raw materials for epoxy resin production are today petroleum derived, although some plant derived sources are now becoming commercially available. Epoxy resins are polymeric or semi-polymeric materials or an oligomer, as such exist as pure substances, since variable chain length results from the polymerisation reaction used to produce them. High purity grades can be produced for certain applications, e.g. using a distillation purification process. One downside of high purity liquid grades is their tendency to form crystalline solids due to their regular structure, which require melting to enable processing. An important criterion for epoxy resins is the epoxide group content; this is expressed as the specific amount of substance of epoxide groups in the material B under consideration, calculated as the ratio of the amount of substance of epoxide groups in this material B, n, divided by the mass m of the material B under consideration, in this case, the mass of the resin.
The SI unit for this quantity multiples thereof. Several deprecated quantities are still in use, including the so-called "epoxide number", not a number and should therefore not be referred to as such, but instead is the ratio of the amount of substance of epoxide groups, n, the mass m of the material B, with the SI unit "mol/kg"; the inverse of the epoxide number is called the "epoxide equivalent weight", the ratio of the mass of a sample B of the resin and the amount of substance of epoxide groups present in that sample B, with the SI unit "kg/mol", is a deprecated quantity. The specific amount of substance of epoxide groups is used to calculate the mass of co-reactant to use when curing epoxy resins. Epoxies are cured with stoichiometric or near-stoichiometric quantities of curative to achieve maximum physical properties; as with other classes of thermoset polymer materials, blending different grades of epoxy resin, as well as use of additives, plasticizers or fillers is common to achieve the desired processing or final properties, or to reduce cost.
Use of blending and fillers is referred to as formulating. Important epoxy resins are produced from combining epichlorohydrin and bisphenol A to give bisphenol A diglycidyl ethers. Increasing the ratio of bisphenol A to epichlorohydrin during manufacture produces higher molecular weight linear polyethers with glycidyl end groups, which are semi-solid to hard crystalline materials at room temperature depending on the molecular weight achieved; this route of synthesis is known as the "taffy" process. More modern manufacturing methods of higher molecular weight epoxy resins is to start with liquid epoxy resin and add a calculated amount of bisphenol A and a catalyst is added and the reaction heated to circa 160 °C; this process is known as "advancement". There are numerous patents and articles on this process, popular for over 20 years; as the molecular weight of the resin increases, the epoxide content reduces and the material behaves more and more like a thermoplastic. High molecular weight polycondensates form a class known as phenoxy resins and contain no epoxide groups.
These resins do however contain hydroxyl groups throughout the backbone, which may undergo other cross-linking reactions, e.g. with aminoplasts and isocyanates. Bisphenol F may undergo epoxy resin formation in a similar fashion to bisphenol A; these resins have lower viscosity and a higher mean epoxy content per gramme than bisphenol A resins, which gives them increased chemical resistance. Reaction of phenols with formaldehyde and subsequent glycidylation with epichlorohydrin produces epoxidised novolacs, such as epoxy phenol novolacs and epoxy cresol novolacs; these are viscous to solid resins with typical mean epoxide functionality of around 2 to 6. The high epoxide functionality of these resins forms a crosslinked polymer network displaying high temperature and chemical resistance, but low flexibility. A related class is cycloaliphatic epoxy resin, which contains one or more cycloaliphatic rings in the molecule (e.g. 3,4-epoxycyclohexylmethyl-3,4-epoxycyc