Carbonate minerals
Carbonate minerals are those minerals containing the carbonate ion, CO32−. Calcite group: trigonal Calcite CaCO3 Gaspeite CO3 Magnesite MgCO3 Otavite CdCO3 Rhodochrosite MnCO3 Siderite FeCO3 Smithsonite ZnCO3 Spherocobaltite CoCO3 Aragonite group: orthorhombic Aragonite CaCO3 Cerussite PbCO3 Strontianite SrCO3 Witherite BaCO3 Rutherfordine UO2CO3 Natrite Na2CO3 Dolomite group: trigonal Ankerite CaFe2 Dolomite CaMg2 Huntite Mg3Ca4 Minrecordite CaZn2 Barytocite BaCa2 Carbonate with hydroxide: monoclinic Azurite Cu322 Hydrocerussite Pb322 Malachite Cu2CO32 Rosasite 2CO32 Phosgenite Pb2Cl2 Hydrozincite Zn526 Aurichalcite 526 Hydromagnesite Mg542.4H2O Ikaite CaCO3·6 Lansfordite MgCO3·5 Monohydrocalcite CaCO3·H2O Natron Na2CO3·10 Zellerite Ca2·5The carbonate class in both the Dana and the Strunz classification systems include the nitrates. IMA-CNMNC proposes a new hierarchical scheme; this list uses the classification of Nickel–Strunz. Abbreviations: "*" – discredited. "?" – questionable/doubtful.
"REE" – Rare-earth element "PGE" – Platinum-group element 03. C Aluminofluorides, 06 Borates, 08 Vanadates, 09 Silicates: Neso: insular Soro: grouping Cyclo: ring Ino: chain Phyllo: sheet Tekto: three-dimensional framework Nickel–Strunz code scheme: NN. XY.##x NN: Nickel–Strunz mineral class number X: Nickel–Strunz mineral division letter Y: Nickel–Strunz mineral family letter ##x: Nickel–Strunz mineral/group number, x add-on letter 05. A Carbonates without additional anions, without H2O 05. AA Alkali carbonates: 05 Zabuyelite. AB Alkali-earth carbonates: 05 Calcite, 05 Gaspeite, 05 Magnesite, 05 Rhodochrosite, 05 Otavite, 05 Spherocobaltite, 05 Siderite, 05 Smithsonite. AC Alkali and alkali-earth carbonates: 05 Eitelite, 10 Nyerereite, 10 Natrofairchildite, 10 Zemkorite. AD With rare-earth elements: 05 Sahamalite-. B Carbonates with additional anions, without H2O 05. BA With Cu, Co, Ni, Zn, Mg, Mn: 05 Azurite, 10 Chukanovite, 10 Malachite, 10 Georgeite, 10 Pokrovskite, 10 Nullaginite, 10 Glaukosphaerite, 10 Mcguinnessite, 10 Kolwezite, 10 Rosasite, 10 Zincrosasite.
BB With alkalies, etc.: 05 Barentsite, 10 Dawsonite, 15 Tunisite, 20 Sabinaite 05. BC With alkali-earth cations: 05 Brenkite, 10 Rouvilleite, 15 Podlesnoite 05. BD With rare-earth elements: 05 Cordylite-, 05 Lukechangite-. BE With Pb, Bi: 05 Shannonite, 10 Hydrocerussite, 15 Plumbonacrite, 20 Phosgenite, 25 Bismutite, 30 Kettnerite, 35 Beyerite 05. BF With, SO4, PO4, TeO3: 05 Northupite, 05 Ferrotychite, 05 Manganotychite, 05 Tychite. C Carbonates without additional anions, with H2O 05. CA With medium-sized cations: 05 Nesquehonite, 10 Lansfordite, 15 Barringtonite, 20 Hellyerite 05. CB With large cations: 05 Thermonatrite, 10 Natron, 15 Trona, 20 Monohydrocalcite, 25 Ikaite, 30 Pirssonite, 35 Gaylussite, 40 Chalconatronite, 45 Baylissite, 50 Tuliokite 05. CC With rare-earth elements: 05 Donnayite-, 05 Mckelveyite-*, 05 Mckelveyite-, 05 Weloganite. D Carbonates with additional anions, with H2O 05. DA With medium-sized cations: 05 Dypingite, 05 Giorgiosite, 05 Hydromagnesite, 05 Widgiemoolthalite.
DB With large and medium-sized cations: 05 Alumohydrocalcite, 05 Para-alumohydrocalcite, 05 Nasledovite.
Conchoidal fracture
Conchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation. Mindat.org defines conchoidal fracture as follows "a fracture with smooth, curved surfaces slightly concave, showing concentric undulations resembling the lines of growth of a shell". Materials that break in this way include quartz, flint, quartzite and other fine-grained or amorphous materials with a composition of pure silica, such as obsidian and window glass, as well as a few metals, such as solid gallium. Conchoidal fractures can occur in other materials under favorable circumstances; this material property was used in the Stone Age to make sharp tools, minerals that fractured in this fashion were traded as a desirable raw material. Conchoidal fractures result in a curved breakage 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. They are defined in contrast to the faceted fractures seen in single crystals such as semiconductor wafers and gemstones, the high-energy ductile fracture surfaces desirable in most structural applications. Several subdefinitions exist, for instance on the Webmineral website: Brittle - conchoidal - brittle fracture producing small, conchoidal fragments Brittle - subconchoidal - brittle fracture with subconchoidal fragments Conchoidal - irregular - irregular fracture producing small, conchoidal fragments Conchoidal - uneven - uneven fracture producing small, conchoidal fragments Subconchoidal - fractures developed in brittle materials characterized by semi-curving surfaces In lithic stone tools, conchoidal fractures form the basis of flint knapping, since the shape of the broken surface is controlled only by the stresses applied, not by some preferred orientation of the material; 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, they can be a useful method of differentiating prehistoric stone tools from natural stones. Fracture The dictionary definition of conchoid at Wiktionary
Lead paint
Lead paint or lead-based paint is paint containing lead. As pigment, lead chromate, Lead oxide, lead carbonate are the most common forms. Lead is added to paint to accelerate drying, increase durability, maintain a fresh appearance, resist moisture that causes corrosion, it is environmental hazards associated with paint. In some countries, lead continues to be added to paint intended for domestic use, whereas countries such as the U. S. and the UK have regulations prohibiting this, although lead paint may still be found in older properties painted prior to the introduction of such regulations. Although lead has been banned from household paints in the United States since 1978, paint used in road markings may still contain it. Alternatives such as water-based, lead-free traffic paint are available, many states and federal agencies have changed their purchasing contracts to buy these instead. Lead white was being produced during the 4th century BC; the traditional method of making the pigment was called the stack process.
Hundreds or thousands of earthenware pots containing vinegar and lead were embedded in a layer of either tan bark or cow dung. The pots were designed so that the vinegar and lead were in separate compartments, but the lead was in contact with the vapor of the vinegar; the lead was coiled into a spiral, placed on a ledge inside the pot. The pot was loosely covered with a grid of lead, which allowed the carbon dioxide formed by the fermentation of the tan bark or the dung to circulate in the pot; each layer of pots was covered by a new layer of tan another layer of pots. The heat created by the fermentation, acetic acid vapor and carbon dioxide within the stack did their work, within a month the lead coils were covered with a crust of white lead; this crust was separated from the lead and ground for pigment. This was an dangerous process for the workmen. Medieval texts warned of the danger of "apoplexy and paralysis" from working with lead white. Despite the risks, the pigment was popular with artists because of its density and opacity.
It was used by artists until the 19th century, when it was replaced by zinc white and titanium white. The dangers of lead paint were considered well-established by the beginning of the 20th century. In the July 1904 edition of its monthly publication, Sherwin-Williams reported the dangers of paint containing lead, noting that a French expert had deemed lead paint "poisonous in a large degree, both for the workmen and for the inhabitants of a house painted with lead colors"; as early as 1886, German health laws prohibited women and children from working in factories processing lead paint and lead sugar. In 1786, Benjamin Franklin wrote a letter warning a friend about the hazards of lead and lead paint, which he considered well-established; the League of Nations began efforts to ban lead paint in 1921. Lead paint is hazardous, it can cause nervous system damage, stunted growth, kidney damage, delayed development. It is dangerous to children because it tastes sweet, therefore encouraging children to put lead chips and toys with lead dust in their mouths.
Lead paint can cause reproductive problems in men or women. Decreases in sperm production in men have been noted. Lead is considered a possible and carcinogen. High levels may result in death; the European Union has passed a directive controlling lead paint use. In Canada, regulations were first enacted under the Hazardous Products Act in 1976 that limited lead content of paints and other liquid coatings on furniture, household products, children's products, exterior and interior surfaces of any building frequented by children to 0.5% by weight. New regulations on surface coating materials, which came into force in 2005, further limit lead to its background level for both interior and exterior paints sold to consumers. Canadian paint manufacturers have been conforming to this background level in their interior and exterior consumer paints since 1991. A Canadian company, Dominion Colour Corporation, is "the largest manufacturer of lead-based paint pigments in the world" and has faced public criticism for obtaining permission from the European Chemicals Agency to continue to export lead chromate paints from its Dutch subsidiary to countries where its uses are not regulated.
The United States' Consumer Product Safety Commission banned lead paint in 1977 in residential properties and public buildings, along with toys and furniture containing lead paint. The cited reason was "to reduce the risk of lead poisoning in children who may ingest paint chips or peelings". For manufacturers, the CPSC instituted the Consumer Product Safety Improvement Act of 2008, which changed the cap on lead content in paint from 0.06% to 0.009% starting August 14, 2009. In 2018 the State of Delaware banned the use of lead paint on outdoor structures. In April 2010 the U. S. Environmental Protection Agency required that all renovators working in homes built before 1978 and disturbing more than six square feet of lead paint inside the home or 20 square feet outside the home be certified. EPA's Lead Renovation and Painting Rule lowers the risk of lead contamination from home renovation activities, it requires that firms performing renovation and painting projects that disturb lead-based paint in homes, child care facilities and pre-schools built before 1978 be certified by EPA and use certified renovators who are trained by EPA-approved training provid
Refractive index
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
Lustre (mineralogy)
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", implies radiance, gloss, or brilliance. A range of terms are used to describe lustre, such as earthy, metallic and silky; the term vitreous refers to a glassy lustre. A list of these terms is given below. Lustre varies over a wide continuum, so there are no rigid boundaries between the different types of lustre; the terms are combined to describe intermediate 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, most notably seen in diamond; such minerals are transparent or translucent, have a high refractive index. Minerals with a true adamantine lustre are uncommon, with examples being cerussite and cubic zirconia. Minerals with a lesser degree of lustre are referred to as subadamantine, with some examples being garnet and corundum.
Dull minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, approximating a Lambertian reflector. An example is kaolinite. A distinction is sometimes drawn between dull minerals and earthy minerals, with the latter being coarser, having less lustre. Greasy minerals resemble grease. A greasy lustre occurs in minerals containing a great abundance of microscopic inclusions, with examples including opal and cordierite, jadeite. Many minerals with a greasy lustre feel greasy to the touch. Metallic minerals have the lustre of polished metal, 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 stilbite. Resinous minerals have the appearance of chewing gum or plastic. A principal example is amber, a form of fossilized resin.
Silky minerals have a parallel arrangement of fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos and the satin spar variety of gypsum. A fibrous lustre has a coarser texture. Submetallic minerals are duller and less reflective. A submetallic lustre occurs in near-opaque minerals with high refractive indices, such as sphalerite and cuprite. Vitreous minerals have the lustre of glass; this type of lustre is one of the most seen, occurs in transparent or translucent minerals with low refractive indices. Common examples include calcite, topaz, beryl and fluorite, among others. Waxy minerals have a lustre resembling wax. Examples include chalcedony. Asterism is the display of a star-shaped luminous area, it is seen in some rubies, where it is caused by impurities of rutile. It can occur in garnet and spinel. Aventurescence is a reflectance effect like that of glitter, it arises from minute, preferentially oriented mineral platelets within the material. These platelets are so numerous that they influence the material's body colour.
In aventurine quartz, chrome-bearing fuchsite makes for a green stone and various iron oxides make for a red stone. Chatoyant minerals display luminous bands; such minerals are composed of parallel fibers, which reflect light into a direction perpendicular to their orientation, thus forming narrow bands of light. The most famous examples are tiger's eye and cymophane, but the effect may occur in other minerals such as aquamarine and tourmaline. Color change is most found in alexandrite, a variety of chrysoberyl gemstones. Other gems occur in color-change varieties, including sapphire, spinel. Alexandrite displays a color change dependent upon light, along with strong pleochroism; the gem results from small-scale replacement of aluminium by chromium oxide, responsible for alexandrite's characteristic green to red color change. Alexandrite from the Ural Mountains in Russia is green by red by incandescent light. Other varieties of alexandrite may be yellowish or pink in daylight and a columbine or raspberry red by incandescent light.
The optimum or "ideal" color change would be fine emerald green to fine purplish red, but this is rare. Iridescence is the'play' or'fire' of rainbow-coloured light caused by thin regular structures or layers beneath the surface of a gemstone. Similar to a thin film of oil on water, these layers interfere with the rays of reflected light, reinforcing some colours and cancelling others. Iridescence is seen at its best in precious opal. Schiller, from German for "color play", is the metallic iridescence originating from below the surface of a stone that occurs when light is reflected between layers of minerals, it is seen in moonstone and labradorite and is similar to adularescence and aventurescence
Light of the Desert
The Light of the Desert is a cerussite gem in the Royal Ontario Museum's collection. It is the world's largest faceted example of cerussite; the word "cerussite" comes from the Latin meaning "white lead". The raw cerussite was discovered in Tsumeb in northern Namibia and acquired by a gem cutter from Arizona who cut the raw material into the gem on display; the cutting and transport of this gem is a delicate business as cerussite is fragile and sensitive to changes in temperature changes and vibration. After it was cut in Arizona, the gem was placed in a box wrapped in a large woolen scarf and a winter vest, hand transported to Toronto for display. Cerussite is too fragile to be set in jewelry. Cerussite is known for its dispersion. Dispersion is the amount of light. Many gem collectors view cerussite favourably because of its ability to prism light into the different colours of the light spectrum
This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Cerussite". Encyclopædia Britannica. 5 (11th ed.). Cambridge University Press. p. 762.
This article incorporates text from a publication now in the 