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absorption line
a dark line in an otherwise uniform and continuous spectrum, resulting from an absorption of photons by a certain element.
anisotropic mineral
a mineral with more than one principal refractive index.
The aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane. The numerical aperture of an optical system is the product of the refractive index n and the sine function of the refraction angle α.
atomic absorption spectroscopy 
a method to determine chemical elements employing the absorption of optical radiation (light) by free atoms in the gaseous state.
an atom or molecule with a negative electrical charge.
the property of a material being directionally dependent, as opposed to isotropy, which implies identical properties in all directions
Calciumsulfatehemihydrate exists in two modifications: α - and β-hemihydrate. β-hemihydrate is formed in dry media, when gypsum is heated over 40°C, while α –hemihydrates is formed in aqueous media when heated over 97.2°C.
a bimodal distribution is a probability distribution with two peaks.
biaxial mineral
Is a mineral with three principal refractive indices and two optic axes. Its indicatrix is a triaxial ellipsoid.
the mathematical difference between the largest and smallest refractive index for an anisotropic mineral
acid-base pair that keeps a relative constant pH value upon dilurion or addition of small amounts of acid or base
an official verification of measurement accuracy of instruments.
Capacitance is a measure of the amount of electrical energy stored (or separated) for a given electric potential: C=Q/V [Farad = F] In a parallel plate capacitor, capacitance is directly proportional to the surface area of the conductor plates and inversely proportional to the separation distance and the material between the plates (dielectric).
an atom or molecule with a positive electrical charge
The CERMET-sensor is a composite material of conductive metal and ceramics to detect the absolute humidity.
Microbes are called chemolithoautotroph, when they are independent from air oxygen (autotroph) and possess the capability gain energy by chemical reaction (chemo) with natural stones (litho), e.g. by oxidation of nitrite to nitrate.
coordination number
The coordination number of a central atom in a molecule or crystal is the number of its nearest neighbors. In many cases the coordination numbers are 3, 4, 6 or 8.
Deutsche Bundesstiftung Umwelt, Osnabrück; one of Europe's largest foundations to promote innovative and exemplary environmental projects.
deliquescence humidity
the relative humidity, above which a material, e.g. a salt, absorbes humidity from the air and dissolves.
see exsiccator
Deutsche Forschungsgemeinschaft, (engl.:German Research Foundation), a research funding organization.
an electric insulator, e.g. the material between the metallic plates of a capacitor.
change of any optical property with wavelength.
When two atoms in a molecule have substantially different electronegativity, one atom attracts electrons more than another, becoming more negative, while the other atom becomes more positive. Such is the case with polar compounds like H2O.
dissociation degree
Dissociation is a general process in which ionic compounds separate or split into two or more electrically neutral particles or ions. For example, NaCl dissociates into Na+ and Cl-. The dissociation degree is the fraction of original solute molecules that have dissociated.
A digital object identifier (DOI) is a character string used to uniquely identify an electronic document.
DynamicPageList is a universal reporting tool for MediaWiki, listing category members and intersections with various formats and details.
Deliquescence Relativ Humidity
Differential Thermal Analysis, a thermoanalytic method to charcterize materials with the help of their heat of reaction.
crystallization of a dissolved salt
carrier liquid or mobile phase of a gas
Environmental Scanning Electron Microscope, a type of scanning electron microscope working without high vacuum.
a container normally made of glas with air-proof lid, in which materials can be dried or moistened with the help of a siccative
Free energy of salvation
Free energy of salvation is the energy released when ions in crystal lattices associate with molecules in a solvent.
File Transport Protocol
gamma radiation
an electromagnetic radiation with short wavelength (10-12m). It is electrically neutral and of negligible mass.
Hochschule für angewandte Wissenschaft und Kunst Hildesheim/Holzminden/Göttingen, University of Applied Sciences and Arts Hildesheim/Holzminden/Göttingen
Inductive Coupled Plasma, method for analysing chemical elements.
describes a measure of opposition to alternating current, comparable with the resistance to direct current in Ohm’s law.
The three-dimensional surface describing the variation in refractive index with relationship to vibration direction of incident light.
interference colours
In physics, interference is the addition of two or more waves that results in a new wave pattern. The colours are produced by the difference in speed in the fast and slow rays. Minerals have specific and predictable colours in cross-polarized light, and this can help identify them.
In chemistry, the term inert is used to describe something that is not chemically reactive. The noble gases are known as inert gases because of their perceived lack of participation in any chemical reactions (e.g. argon).
isotropic mineral
A mineral with the same refractive index regardless of vibration direction. Its indicatrix is asphere.
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom.
concentration given as amount of substance (mol) of the dissolved substance per kilogram solvent; unit: mol•kg-1.
A molecule is an electrically neutral group of at least two atoms.
In physics, monochromatic refers to electromagnetic radiation of a single frequency.
optic axis
of a crystal: a thought axis in the Dupin indicatrix
optical class
One of five possible classes (different indicatrices) to which a mineral can belong: isotropic, uniaxial +/-, or biaxial +/-.
optical orientation
The relationship between a mineral's crystallographic axes and optical indicatrix.
optical path difference
when a lightray is split into two rays of different speed in a birefringent crystal, they reach the end of the crystal after a different length of time. The resulting delay is called optical path difference.
Peltier element
A peltier element causes cooling due to the peltier effect (peltier cooling).
Peltier cooling
The Peltier effect is the presence of a temperature difference at an electrified junction of two different metals. This is used e.g. in cooling devices in refrigerators.
The permeability is a measure of the ability of a porous material (often a rock or unconsolidated material) to allow fluids to pass through it. Am material with a high permeability lets the fluid pass through faster than one with a low permeability.
A phase is a physically distinctive form of matter and is characterized by having relatively uniform chemical and physical properties.
plane of symmetry
A plane of symmetry is a thought plane in a crystal, on which the components of the crystal are reflected.
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. A very high heating over a few thousand K leads to ionization, thus turning it into a plasma, containing charged particles.
the property of exhibiting different colors as a function of the vibration direction
point of symmetry
The point of symmetry is in the centre of a crystal, where its components are reflected to the opposite side.
polarised light
Light is called polarised, when the oscillation of the light waves has a certain orientation. The electric field may be oriented in a single direction (linear polarization), or it may rotate as the wave travels (circular or elliptical polarization) This can be achieved by using polarising filters. Natural daylight is not polarized.
principal refractive index
for isotropic minerals -n, for uniaxial minerals - e and w, for biaxial minerals - a, b, and g
Psychrometric means the determination of relative humidity with a psychrometer.
quality managemnet
Responding behaviour
the responding behaviour of a sensor describes the time it needs to show the right value. It is characterized by two step responses: the half-value period t05 and the nine-tenth-value period t09. T05 indicates, after which period 50%, and t09 indicates, when 90% of the measuring value are achieved.
retention time
is the time required by each of the individual ions, i.e., the analyte, for passing through the column from injection to detection point
relative humidity
screw dislocation
a screw dislocation is a defect or irregularity within a crystal structure.
Scanning Electron Microscope
Technische Informationsbibliothek Hannover: German National Library for Science and Technology in Hannover
uniaxial mineral
A mineral with two principal refractive indices and one optic axis. Its indicatrix is a prolate or oblate ellipsoid.
uniform resource number
valence electrons
Valence electrons are the electrons on the outer shell of an atom that can participate in the formation of chemical bonds with other atoms.
water glass
Water glass is the common name for a liquid solution of alkaline silicates, also known as Sodium silicate Na2SiO3 or liquid glass.
X-ray diffraction
Zeta potential
Zeta potential is the electric potential difference in the interfacial double layer between the dispersion medium and the stationary layer of fluid attached to the dispersed particle.