QuartzQuartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at .
OpalOpal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt.
ChertChert ('tʃɜrt) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. Chert is typically composed of the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor, and which contains the silicon skeletal remains of diatoms, silicoflagellates, and radiolarians.
Silicon dioxideSilicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, opal and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries.
AusteniteAustenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures. The austenite allotrope is named after Sir William Chandler Roberts-Austen (1843–1902); it exists at room temperature in some stainless steels due to the presence of nickel stabilizing the austenite at lower temperatures.
Iron oreIron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the form of magnetite (Fe3O4, 72.4% Fe), hematite (Fe2O3, 69.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH)·n(H2O), 55% Fe) or siderite (FeCO3, 48.2% Fe). Ores containing very high quantities of hematite or magnetite, typically greater than about 60% iron, are known as natural ore or direct shipping ore, and can be fed directly into iron-making blast furnaces.
CristobaliteCristobalite (krɪˈstoʊbəˌlaɪt) is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group, which also include coesite, tridymite and stishovite. It is named after Cerro San Cristóbal in Pachuca Municipality, Hidalgo, Mexico. It is used in dentistry as a component of alginate impression materials as well as for making models of teeth.
Biogenic silicaBiogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants. Silica is an amorphous metal oxide formed by complex inorganic polymerization processes. This is opposed to the other major biogenic minerals, comprising carbonate and phosphate, which occur in nature as crystalline iono-covalent solids (e.g.
Fumed silicaFumed silica (CAS number 112945-52-5), also known as pyrogenic silica because it is produced in a flame, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk density and high surface area. Its three-dimensional structure results in viscosity-increasing, thixotropic behavior when used as a thickener or reinforcing filler.
Amorphous solidIn condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a glass transition. Examples of amorphous solids include glasses, metallic glasses, and certain types of plastics and polymers. The term comes from the Greek a ("without"), and morphé ("shape, form").
Amorphous metalAn amorphous metal (also known as metallic glass, glassy metal, or shiny metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity and can show metallic luster.
Raman spectroscopyRaman spectroscopy (ˈrɑːmən) (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified. Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering.
BainiteBainite is a plate-like microstructure that forms in steels at temperatures of 125–550 °C (depending on alloy content). First described by E. S. Davenport and Edgar Bain, it is one of the products that may form when austenite (the face-centered cubic crystal structure of iron) is cooled past a temperature where it is no longer thermodynamically stable with respect to ferrite, cementite, or ferrite and cementite. Davenport and Bain originally described the microstructure as being similar in appearance to tempered martensite.
IronIron is a chemical element with the symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, just ahead of oxygen (32.1% and 30.1%, respectively), forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust, being mainly deposited by meteorites in its metallic state, with its ores also being found there.
Silica gelSilica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum. In the last case, the material is properly called silica xerogel. Silica xerogel with an average pore size of 2.4 nanometers has a strong affinity for water molecules and is widely used as a desiccant.
Sampling (statistics)In statistics, quality assurance, and survey methodology, sampling is the selection of a subset or a statistical sample (termed sample for short) of individuals from within a statistical population to estimate characteristics of the whole population. Statisticians attempt to collect samples that are representative of the population. Sampling has lower costs and faster data collection compared to recording data from the entire population, and thus, it can provide insights in cases where it is infeasible to measure an entire population.
Silica cycleThe silica cycle is the biogeochemical cycle in which biogenic silica is transported between the Earth's systems. Silicon is considered a bioessential element and is one of the most abundant elements on Earth. The silica cycle has significant overlap with the carbon cycle (see carbonate–silicate cycle) and plays an important role in the sequestration of carbon through continental weathering, biogenic export and burial as oozes on geologic timescales.
Iron meteoriteIron meteorites, also called siderites or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron meteorites originate from cores of planetesimals, with the exception of the IIE iron meteorite group The iron found in iron meteorites was one of the earliest sources of usable iron available to humans, due to the malleability and ductility of the meteoric iron, before the development of smelting that signaled the beginning of the Iron Age.
KyaniteKyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite, and the presence of kyanite in metamorphic rocks generally indicates metamorphism deep in the Earth's crust. Kyanite is also known as disthene or cyanite. Kyanite is strongly anisotropic, in that its hardness varies depending on its crystallographic direction. In kyanite, this anisotropism can be considered an identifying characteristic, along with its characteristic blue color.
Alloy steelAlloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low alloy steels and high alloy steels. The difference between the two is disputed. Smith and Hashemi define the difference at 4.0%, while Degarmo, et al., define it at 8.0%. Most commonly, the phrase "alloy steel" refers to low-alloy steels. Strictly speaking, every steel is an alloy, but not all steels are called "alloy steels".
