"static press or using explosives. It has also been produced by chemical vapor deposition, and also by the thermal decomposition of a polymer, poly(hydridocarbyne), at atmospheric pressure, under argon atmosphere, at . It is translucent, brownish-yellow, and has an index of refraction of 2.40 to 2.41 and a specific gravity of 3.2 to 3.3. Its hardness is theoretically superior to that of cubic diamond (up to 58% more), according to computational simulations, but natural specimens exhibited somewhat lower hardness through a large range of values (from 7 to 8 on Mohs hardness scale). The cause is speculated as being due"
"Topaz Topaz is a silicate mineral of aluminium and fluorine with the chemical formula AlSiO(F, OH). Topaz crystallizes in the orthorhombic system, and its crystals are mostly prismatic terminated by pyramidal and other faces. It is one of the hardest naturally occurring minerals (Mohs hardness of 8) and is the hardest of any silicate mineral. This hardness combined with its usual transparency and variety of colors means that it has acquired wide use in jewellery as a cut gemstone as well as for intaglios and other gemstone carvings. Topaz in its natural state is a golden brown to yellow, a"
"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 (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum. The table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate (unglazed porcelain) has a hardness of approximately 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"
"these translations as ""topaz"" all derive from the Septuagint translation ""topazi[os]"", which as mentioned above referred to a yellow stone that was not topaz, but probably ""chrysolite"" (chrysoberyl or peridot), it should be borne in mind that topaz is likely not meant here. An English superstition held that topaz cured lunacy. Topaz Topaz is a silicate mineral of aluminium and fluorine with the chemical formula AlSiO(F, OH). Topaz crystallizes in the orthorhombic system, and its crystals are mostly prismatic terminated by pyramidal and other faces. It is one of the hardest naturally occurring minerals (Mohs hardness of 8) and is"
"harder. This became the basis of the hardness scale developed by Mohs. The hardest mineral, diamond was given a value of 10 and softer minerals such as talc were given the very low value of 1 (unity). Other minerals were given intermediate values, depending on their ability to scratch another mineral in the scale. Thus gypsum was given the value 2 because it will scratch talc crystals, and calcite the value 3 because it will scratch gypsum. Minerals are also now classified by chemical characteristics, but the physical properties are still useful in field examination. In 1812, Mohs became a"
"various areas including the Ural and Ilmen mountains of Russia, in Afghanistan, Sri Lanka, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico; Flinders Island, Australia; Nigeria and the United States. Brazil is one of the largest producers of topaz, some clear topaz crystals from Brazilian pegmatites can reach boulder size and weigh hundreds of pounds. The Topaz of Aurangzeb, observed by Jean Baptiste Tavernier weighed 157.75 carats. The American Golden Topaz, a more recent gem, weighed a massive 22,892.5 carats. Large, vivid blue topaz specimens from the St. Anns mine in Zimbabwe were found in the late 1980s."
"very hard, topaz must be treated with greater care than some other minerals of similar hardness (such as corundum) because of a weakness of atomic bonding of the stone's molecules along one or another axial plane (whereas diamonds, for example, are composed of carbon atoms bonded to each other with equal strength along all of its planes). This gives topaz a tendency to fracture along such a plane if struck with sufficient force. Topaz has a relatively low index of refraction for a gemstone, and so stones with large facets or tables do not sparkle as readily as stones cut"
"Washington, D.C.. American Golden Topaz The American Golden Topaz, a 172-faceted topaz weighing , is the largest cut yellow topaz in the world, and one of the largest faceted gems of any type in the world. Originating from Minas Gerais, Brazil, it was cut by Leon Agee over a period of two years from an 11.8 kg (26 lb avdp) stream-rounded cobble owned by Drs. Marie L. and Edgar F. Borgatta. It was contributed jointly by the Borgatta owners and by Rockhound Hobbyists of America to the Smithsonian Institution in 1988 and is displayed in the National Museum of Natural"
"necessarily constant for all sides, which is a function of its structure; crystallographic weakness renders some directions softer than others. An example of this property exists in kyanite, which has a Mohs hardness of 5½ parallel to [001] but 7 parallel to [100]. The most common scale of measurement is the ordinal Mohs hardness scale. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc, a phyllosilicate, to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below: Lustre indicates how light reflects from the mineral's"
"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 seeing which minerals can visibly scratch others is, however, 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."
"American Golden Topaz The American Golden Topaz, a 172-faceted topaz weighing , is the largest cut yellow topaz in the world, and one of the largest faceted gems of any type in the world. Originating from Minas Gerais, Brazil, it was cut by Leon Agee over a period of two years from an 11.8 kg (26 lb avdp) stream-rounded cobble owned by Drs. Marie L. and Edgar F. Borgatta. It was contributed jointly by the Borgatta owners and by Rockhound Hobbyists of America to the Smithsonian Institution in 1988 and is displayed in the National Museum of Natural History in"
"Scratch hardness Scratch hardness tests are used to determine the hardness of a material to scratches and abrasion. The earliest test was developed by mineralogist Friedrich Mohs in 1820 (see Mohs scale). It is based on relative scratch hardness, with talc assigned a value of 1 and diamond assigned a value of 10. Mohs' scale had two limitations; it was not linear, and most modern abrasives fall between 9 and 10. Raymond R. Ridgway, a research engineer at the Norton Company, modified the Mohs scale by giving garnet a hardness of 10 and diamond a hardness of 15. Charles E."
"a silvery-grey metal with a Mohs hardness of 5.5, and a standard atomic weight of 95.95 g/mol. It has a melting point of ; of the naturally occurring elements, only tantalum, osmium, rhenium, tungsten, and carbon have higher melting points. It has one of the lowest coefficients of thermal expansion among commercially used metals. The tensile strength of molybdenum wires increases about 3 times, from about 10 to 30 GPa, when their diameter decreases from ~50–100 nm to 10 nm. Molybdenum is a transition metal with an electronegativity of 2.16 on the Pauling scale. It does not visibly react with"
"is colorless to white, transparent to translucent. The streak is white and the luster is vitreous. Cleavage on {100} is perfect, no parting is observed, and fracture is uneven as tumchaite is very brittle. The Mohs hardness is 4.5, between fluorite and apatite. The Vickers hardness test yielded 365 to 445- averaging 410- kg/mm with a 40 g load. The density, which was determined by flotation of the mineral using a dilute Clerici-HO solution, was 2.78 (2) g/cm versus the 2.77 g/cm determined by the empirical formula. Subbotin, et al., performed quantitative electron microprobe analysis with MS 46 CAMECA instrument"
"incorporates additional substances that may fall between levels: Comparison between hardness (Mohs) and hardness (Vickers): 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 seeing which minerals can visibly scratch others is, however, of great antiquity, having been mentioned by Theophrastus in his treatise"
"very soft metal with a Mohs hardness of 1.5; it can be scratched with a fingernail. It is quite malleable and somewhat ductile. The bulk modulus of lead—a measure of its ease of compressibility—is 45.8 GPa. In comparison, that of aluminium is 75.2 GPa; copper 137.8 GPa; and mild steel 160–169 GPa. Lead's tensile strength, at 12–17 MPa, is low (that of aluminium is 6 times higher, copper 10 times, and mild steel 15 times higher); it can be strengthened by adding small amounts of copper or antimony. The melting point of lead—at 327.5 °C (621.5 °F)—is very low compared"
"Monazite Monazite is a reddish-brown phosphate mineral containing rare-earth metals. It occurs usually in small isolated crystals. It has a hardness of 5.0 to 5.5 on the Mohs scale of mineral hardness and is relatively dense, about 4.6 to 5.7 g/cm. There are at least four different kinds of monazite, depending on relative elemental composition of the mineral: The elements in parentheses are listed in the order of their relative proportion within the mineral: lanthanum is the most common rare-earth element in monazite-(La), and so forth. Silica (SiO) is present in trace amounts, as well as small amounts of uranium"
"jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs). Sapphire is the birthstone for September and the gem of the 45th anniversary."
"however, higher electrical conductivity and birefringence of moissanite may alert a buyer to fraud. In addition, thermochromism is exhibited in moissanite, such that heating it gradually will cause it to change color starting at around . This color change can be diagnostic for distinguishing diamond from moissanite, although birefringence and electrical conductivity differential are more practical diagnostic differentiators. On the Mohs scale of mineral hardness it is a 9.5, with a diamond being a 10. In many developed countries, the use of moissanite in jewelry was controlled by the patents held by Charles & Colvard; these patents expired in August"
"classified into density (often given as specific gravity); measures of mechanical cohesion (hardness, tenacity, cleavage, fracture, parting); macroscopic visual properties (luster, color, streak, luminescence, diaphaneity); magnetic and electric properties; radioactivity and solubility in hydrogen chloride (). ""Hardness"" is determined by comparison with other minerals. In the Mohs scale, a standard set of minerals are numbered in order of increasing hardness from 1 (talc) to 10 (diamond). A harder mineral will scratch a softer, so an unknown mineral can be placed in this scale by which minerals it scratches and which scratch it. A few minerals such as calcite and kyanite"
"(""proper"", ""unalterable"", ""unbreakable"") and sometimes called adamant, diamond is the hardest known naturally occurring material, scoring 10 on the Mohs scale of mineral hardness. Diamond is extremely strong owing to the structure of its carbon atoms, where each carbon atom has four neighbors joined to it with covalent bonds. The material boron nitride, when in a form structurally identical to diamond (zincblende structure), is nearly as hard as diamond; a currently hypothetical material, beta carbon nitride, may also be as hard or harder in one form. It has been shown that some diamond aggregates having nanometer grain size are harder"
"have a hardness that depends significantly on direction. Hardness can also be measured on an absolute scale using a sclerometer; compared to the absolute scale, the Mohs scale is nonlinear. ""Tenacity"" refers to the way a mineral behaves when it is broken, crushed, bent or torn. A mineral can be brittle, malleable, sectile, ductile, flexible or elastic. An important influence on tenacity is the type of chemical bond (""e.g.,"" ionic or metallic). Of the other measures of mechanical cohesion, ""cleavage"" is the tendency to break along certain crystallographic planes. It is described by the quality (""e.g."", perfect or fair) and"
"alloy is a hardness of 120 HV, a yield strength of 300 MPa, a tensile strength of 330 MPa and a stiffness of 85 GPa. These values are about 25% higher than those for the base alloy. Dr Cem Selcuk, project manager for Adal, said in their September 19, 2005 news release, ""Just for comparison with another strong material, white cast iron has a tensile strength of approximately 250 MPa (Mega Pascals)""[sic]"" and is also brittle, whereas ticalium has a higher strength of about 330 MPa together with a greater stiffness while exhibiting greater lightness according to third party testing."""
"6 and 7 on the Mohs hardness scale, and its specific gravity ranges from 3.10 to 3.38, depending on the variety. It streaks white and is said to be brittle. Clinozoisite is a more common monoclinic polymorph of CaAl(SiO)(SiO)O(OH). Transparent material is fashioned into gemstones while translucent-to-opaque material is usually carved. The mineral was described by Abraham Gottlob Werner in 1805. He named it after the Carniolan naturalist Sigmund Zois, who sent him its specimens from Saualpe in Carinthia. Zois realized that this was an unknown mineral when it was brought to him by a mineral dealer, presumed to be"
"any mineral. Its mean refractive index is 3.08 (sodium light wavelengths), versus the indices for diamond and the non-mineral gallium(III) arsenide (GaAs), which are 2.42 and 3.93, respectively. The hardness of cinnabar is 2.0–2.5 on the Mohs scale, and its specific gravity 8.1. Structurally, cinnabar belongs to the trigonal crystal system. It occurs as thick tabular or slender prismatic crystals or as granular to massive incrustations. Crystal twinning occurs as simple contact twins. Note, mercury(II) sulfide, HgS, adopts the cinnabar structure described, and one additional structure, i.e. it is dimorphous. Cinnabar is the more stable form, and is a structure"
"tools, or cermet. Tantalcarbide Tantalcarbide is a rare mineral of tantalum carbide with formula TaC. With a molecular weight of 192.96 g/mol, its primary constituents are tantalum (93.78%) and carbon (6.22%), and has an isometric crystal system. It generally exhibits a bronze or brown to yellow color. On the Mohs hardness scale it registers as a 6-7. Tantalcarbide is generally found in a granular state. It is extremely dense at 14.6 g/formula_1. Sub-conchoidal fracturing is exhibited. Specimens are extremely rare in nature. It is the only known mineral to exhibit the composition of TaC. Tantalum carbide powder is used for"
"Tombac Tombac, as it is spelled in French, or tombak, is a brass alloy with high copper content and 5–20% zinc content. Tin, lead or arsenic may be added for colouration. It is a cheap malleable alloy mainly used for medals, ornament, decoration and some munitions. In older use, the term may apply to brass alloy with a zinc content as high as 28–35%. The term ""tombak"" is derived from ""tembaga"", an Indonesian/Malay word of Javanese origin meaning copper. ""Tembaga"" entered Dutch usage concurrent with their colonisation of Indonesia. Likely, the term was used generically to describe Indonesian high-copper brass"
"hardness scale (VHN hardness of 38). There is no discernible type of cleavage, but due to the small size of the crystallites the possibility of cleavage can't be 100% excluded. It is a rather dense mineral weighing in at 6.541 g/cm. The data for this chart was gathered using a polished section by electron microprobe and using a crystal spectrometer with the following standards: galena (S), cinnabar (Hg), and metals (Ag and Cu). The results were calculated on the basis of 23 atoms due to its chemical formula being very similar to balkanite. The sample found was ground up and"
"1/2 ounce of zinc to the pound [sic: copper?]"" Typical tempers are soft annealed and rolled hard. Tombac is easy and soft to work by hand: hand tools can easily punch, cut, enamel, repousse, engrave, gild, or etch it. It has a higher sheen than most brasses or copper, and does not easily tarnish. Historically, it was used by the Javanese as a ""faux"" gold finish for ""objects d'art"" and ornaments. Tombac Tombac, as it is spelled in French, or tombak, is a brass alloy with high copper content and 5–20% zinc content. Tin, lead or arsenic may be added"
"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, white, beige, or somewhat green, yellow, or red. The crystals tend to be long thin blades that typically form radial aggregates, and sometimes fans and tufts. The aggregates are variable and may be spikey in appearance, dense and ball-like, or"
"Faustite The IMA approved mineral faustite, named after the American mineralogist and petrologist with the U.S. Geological Survey (USGS) Dr. George Tobias Faust, is a member of the triclinic turquoise group of hydrous phosphates with the following chemical composition: ZnAl(PO)(OH)·4HO Some divalent copper generally replaces the zinc position. Faustite is the zinc rich analogue of turquoise having almost four times as much zinc than copper in its crystal structure. Trivalent (ferric) iron may replace some of the aluminum. Minor amounts of calcium may also be present. It has a hardness of 4.5 - 5.5 on the Mohs scale of mineral"
"which can be leveraged for explosive purposes. Phosphorus in its most thermodynamically stable black form, is a lustrous and comparatively unreactive solid with a density of 2.69 g/cm, and is soft (MH 2.0) and has a flaky comportment. It sublimes at 620 °C. Black phosphorus has an orthorhombic crystalline structure (CN 3). It is a semiconductor with a band gap of 0.3 eV. It has a high ionisation energy (1086.5 kJ/mol), moderate electron affinity (72 kJ/mol), and moderate electronegativity (2.19). In comparison to nitrogen, phosphorus usually forms weak hydrogen bonds, and prefers to form complexes with metals having high electronegativities,"
"in northern Brazilian coastal areas, from south Bahia to Guarapari, a city with highly radioactive monazite sand beaches, with radiation levels up to 50 times higher than world average background radiation. Thorium Thorium is a weakly radioactive metallic chemical element with symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided. All"