Mineral

A mineral ( from Medieval- aes minerals " Grubenerz " was coined in the 16th century after the French model, . Majority of minerals or mineral ) is an element or a chemical compound that has been generally crystalline, formed through geological processes.

The majority of known today by the International Mineralogical Association (IMA ) as an independently recognized around 4,800 minerals is inorganic, but also some organic substances such as mellit and Evenkit or Nierensteinbildner Whewellite and Weddellit are recognized as minerals because they are also formed naturally. Including all known mineral varieties and synonymous terms, however, there are more than 5,500 mineral name.

The doctrine of the minerals is the mineralogy of their use and processing the Lithurgik.

5.1 Optical Properties
5.2 Mechanical properties
5.3 Magnetic Properties
5.4 Electrical Properties
5.5 Chemical Properties
5.6 odor properties
5.7 flavor characteristics
5.8 Other properties

6.1 Petrological significance
6.2 Lagerstättenkundliche importance
6.3 Gemmological importance
6.4 Other Meaning

Deferrals and exemptions

Homogeneity

The terms " chemical element " and " chemical compound " includes a solid composition and a defined chemical structure. Mixtures are not minerals. However, the compositions of minerals can have a certain variation ( solid solution ), as long as they are structurally homogeneous.

A chemical compound can occur with various structures. Chemically defined mixtures of different phases of different structure are also no minerals. Thus, for example flint ( chert ) are made of pure SiO2, but is not a mineral but a mixture of structurally different minerals deep quartz, opal and Moganite and thus a rock.

Crystallinity

Some naturally occurring compounds are not crystalline. These substances can be divided into two categories:

Amorphous: These are substances that were never crystalline.
Mitamikt: Formerly crystalline substances whose long-range order is destroyed by nuclear radiation.

The determination of the structure and composition of a complete, sufficient to clearly distinguish amporphe phases from each other, is usually difficult if not impossible. Therefore, non-crystalline natural compounds by many scientists, the term Mineraloide are summarized.

Natural amorphous substances can be recognized as a mineral if the following conditions are met:

Complete chemical analysis, covering the entire compositional range of the substance
Physicochemical ( spectroscopic ) data demonstrating the uniqueness of the substance
The substance can not be converted (eg heating ) in a crystalline state by physical treatment.

Examples are Georgeit and Calciouranoit.

Metamikte substances can be minerals, it can be shown that the substance originally was crystalline and had the same composition (eg fergusonite -Y).

Liquids are not generally counted among the minerals. Liquid water, for example, is not a mineral, ice does. An exception is mercury: It comes as element on earth only liquid and gaseous form, it is also recognized as a liquid but as a mineral. Petroleum and all other, and solid non-crystalline mixtures and bitumen are no minerals.

Extraterrestrial substances

The processes that contribute to the formation of extraterrestrial substances, such as meteorites and lunar rocks are similar to those that take place on Earth. Occurring components of extraterrestrial rocks and cosmic dust As a result, of course, referred to as minerals (eg Tranquillityit, Brownleeit ).

Anthropogenic substances

Substances produced by humans are not minerals. If such anthropogenic substances are identical with minerals, they are referred to as " synthetic equivalent ".

Also materials that are caused by geological processes of synthetic materials are generally not referred to as minerals. An exception are some substances that have previously been recognized as minerals, such as some minerals that have formed in the reaction of ancient metallurgical slags with seawater.

Natural substances that have been transformed by human activities can be recognized as minerals if human activities were not directly aimed at the production of new substances. Substances that are newly formed during mine fires, however, no minerals are.

Biogenic substances

Biogenic substances are compounds that have been formed exclusively by biological processes without a geological component, such as shells or oxalate crystals in plant tissues. These compounds are not minerals.

Once geological processes were involved in the formation of compounds, these substances can be recognized as minerals. Examples include minerals which have formed from organic matter in black shales or from bat guano in caves, as well as components of limestones and phosphorites of organic origin.

Occurrence

With the exception of natural glasses and the coal rocks all rocks of the earth and other celestial bodies from minerals are constructed. Most commonly about thirty minerals occur, the so-called Gesteinsbildner. In addition, you will find minerals as colloids in the water or as fine dust in the air. Also water itself is a mineral when it is in the form of water ice.

Mineral formation

Minerals formed by crystallisation from melt ( igneous mineral formation ), aqueous solutions ( hydrothermal and sedimentary mineral formation ) and from the air ( sublimation of gases, for example, volcanoes ) or during metamorphosis by solid state reactions of other minerals or natural glasses. Primary minerals emerged in parallel with the rock, which they are part, while the formation of secondary minerals by a subsequent change in the rock ( metamorphism, hydrothermal overprinting or weathering ).

There are two stages of mineral formation: First, more atoms or ions accumulate together and form a nucleation ( nucleation ). If this exceeds a critical nucleus radius, he continues to grow and there is a mineral (crystal growth). Finally, after numerous conversion reactions with other minerals, with the air or the water is destroyed by the weathering of minerals. The ions that make up the crystal lattice was built, go back into solution or arrive at the anatexis in a molten rock ( magma ). Finally, the cycle begins at a different location from the front.

To determine the Abkühlalters see fission tracks.

A special form of mineral formation from solution is the biomineralization. This refers to the formation of minerals by organisms. The following minerals can arise in this way:

Hydroxyapatite builds the bones of all vertebrate animals and together with fluorapatite the enamel of mammals on.
Magnetite is a series of living beings as a compass for orientation in the geomagnetic field. This has been first observed in magnetotactic bacteria. It is now also known from insects, mollusks, fish, birds and mammals.

Other forms of mineral formation from solution or by the reaction of minerals with water play a role in the Technical Mineralogy:

Calcite is used to neutralize acids including carbonic acid to form water hardness, pyrite acts as a reducing agent in bacterial elimination of nitrate by denitrification, while clay minerals neutralization reactions can cause at low pH values and ionic exchange reactions. In drinking water treatment arise as reaction products in the elimination of iron ( II) - and manganese ions goethite and δ - MnO2, calcite can at Enthärtungsreaktionen ( decarbonisation ) are formed. In waste water treatment, water- clear crystals of struvite, an ammonium magnesium phosphate, occur at a sufficiently high phosphate concentrations in the waste water treatment plants. This can reduce the cross -section of lines. In the corrosion of steel and cast iron in contact with water greigite may vary depending on water quality goethite, magnetite and lepidocrocite, at higher alkalinity and siderite, vivianite in phosphate- containing waters, in sulfate -containing waters troilite and in hydrogen sulfide-containing waters are formed. From copper to cuprite, malachite or azurite can make as lead mainly Hydrocerussite arises.

Crystallography

Free crystallized minerals show externally a geometric shape with defined natural areas that relate to each other in fixed angular relationships, depending on the specific crystal system, which is associated with the mineral. This is also known as the law of constant angles ( Nicolaus Steno, 1638-1686 ). The symmetrical arrangement of the surfaces is an expression of the internal structure of a crystalline mineral: It shows a well-ordered atomic structure, which is formed by many repeated juxtaposition of so-called elementary cells that make up the smallest structural unit of the mineral. Due to the internal symmetry A distinction is six to seven crystal systems, namely the cubic, hexagonal, trigonal, tetragonal, orthorhombic, the, the monoclinic and triclinic the system. The hexagonal and the trigonal system are summarized occasionally by some mineralogists. Two or more mineral individuals that have grown in a specific crystallographic orientation together are called twins. They are formed during growth or during the deformation of the rock. Multiple twins often form so-called twin lamellae, which must not be confused with the exsolution lamellae, which arise when a solid solution is thermodynamically unstable during cooling and the formation of precipitates.

Properties

Optical Properties

Determine with the naked eye:

Color: A distinction idiochromatische minerals ( for example, Cinnabar ), which are colored by the formula effective elements, allochromatische minerals (eg quartz), which often have different colors result from different trace elements and defects of the crystal lattice, and pseudochromatische minerals whose colors like opals caused by light refraction or interference. In the ore microscopy always one sees the complementary color of the real color since you are working in reflected light. The color in minerals resulting from the absorption of light of the complementary color of one or more of the following processes: Transitions of electrons between the split by the crystal field d- or f - orbitals of the transition metals or lanthanides (eg, the red color of the ruby by chromium ions on the aluminum position)
Transitions of electrons between two cations or between cation and anion (eg, the blue color of the sapphire by transitions between titanium and Eisenverunreinungen )
Transitions of electrons from the valence band into the conduction band of semiconductors (for example, the red color of the Cinnabarits )
Transitions of electrons from the valence band to the acceptor level of contamination (eg blue color of diamond because of boron)
Transitions of electrons from the donor level of an impurity in the conduction band (for example, yellowing of the diamond due to nitrogen)
Transitions of electrons between s- and d- bands in conductors (eg color of gold )
Change in the energy state of an electron on an anion vacancy
Diffraction effects on low-dimensional structures (eg Opal)

Determination with polarized light microscopy in transmitted light:

Pleochroism: Some minerals transparent colors and color depths in different directions are different. Show two colors this is called dichroism in three colors trichroism or pleochroism. The term is also used as a collective term for both types of multi color.
Refractive index: ratio of the speed of light in air to the speed of light in the mineral is determined by immersion methods, approximated by the strength of the relief and the motion of the Becke'schen line, a bright line at a grain boundary, while moving the microscope stage. Here, the mnemonic applies: Down ( to the table ), higher ( mineral with the higher light refraction than the neighboring mineral ) into (movement of Becke'schen line).
Birefringence: The difference in refractive indices in the different directions of the crystal. It is determined under crossed polarizers with the help of color charts from the interference color.

Determination with polarized light microscopy in reflected light ( ore microscopy ):

Reflectance: fraction of the reflected light. Determination by ore microscopy. Characteristic for the distinction of gold from sulfide minerals.
Bireflektanz: directionality of the color in the ore microscopy, which can be seen under a polarizer.
Anisotropy: Under crossed polarizers observable in the ore microscopy color phenomena in opaque minerals.
Internal reflections: Diffuse reflection of light at interfaces to impurities, which corresponds to the stroke color and under crossed polarizers is best visible in dark position.

Determination with special microscopes:

Luminescence: Some minerals emit light when you experience a whatever type of excitation. By type of excitation, a distinction chemiluminescence Triboluminescence, cathodoluminescence and thermoluminescence, the type of light emitted UV, VIS and IR luminescence. Short luminescence is called fluorescence, longer-lasting phosphorescence.

Mechanical properties

Density: It depends on the chemical composition and structure. The density of minerals, rocks and ores varies 1 to 20 values below 2 are as easily perceived (Bernstein 1.0 ), those of 2 to 4 as normal ( quartz 2.6 ) and those above 4 appear to us as heavy ( galena 7.5). Minerals with a density of > 3.0 are called heavy minerals. The density separation is an important treatment method. If the density relative to the density of water, so it is called relative density o and is then unitless.
Hardness: It is determined by the stability of the chemical bonds in the mineral and determined by their resistance to scratching. It is given in mineralogy by its value on the Mohs scale, which ranges from 1 ( very soft, talc ) to 10 ( very hard as diamond ).
Cleavage: tendency of a mineral to split along certain crystallographic planes. It fails to distinguish existing cleavage (eg quartz), indistinct cleavage (for example beryl ), significant cleavage (eg apatite ), good cleavage (eg diopside ), perfect cleavage (eg sphalerite ) and highly perfect cleavage (eg mica ). It describes crystal planes, between which there are only weak forces and to which, therefore, the crystal can be cleaved. For example, calcite has three cleavage planes and is so very perfect cleavage. Contrast, quartz has no cleavage plane.
Fracture behavior: Aborts a mineral not along its cleavage planes, often occur on characteristic fracture structures. A distinction is conchoidal fracture (eg quartz), fibrous fracture (eg kyanite ), splintery fracture (eg, chrysotile ), planar fracture and uneven fracture.
Toughness or tenacity: A distinction is brittle minerals (eg quartz) of flexible (eg muscovite ).

Magnetic Properties

Magnetism: A distinction ferromagnetic minerals (eg iron), ferrimagnetic minerals (eg magnetite), paramagnetic minerals (eg biotite ), diamagnetic minerals (eg quartz) and antiferromagnetic minerals (eg hematite). Usually, only ferrous and ferric magnetism with the help of a compass needle to be determined.

Electrical properties

Conductivity: Most minerals are insulators, some sulfides and oxides are semiconductors, dignified metals are conductors. Covellite is having a transition temperature of 1.63 Kelvin, the only known naturally occurring mineral superconductors.
Piezoelectricity: for example, ability of the crystal to convert a mechanical vibration into an AC voltage and vice versa.
Pyroelectricity: ability, for example, the tourmaline to convert a temperature difference in a charge separation.

Chemical Properties

Flame coloration: Some items discolor a flame. This property is used in the flame test, to infer the chemical composition of the mineral. Gas burners are best suited in darkened rooms.
Fusibility: it describes the behavior before the blowpipe, so the melting reaction.
Reaction with hydrochloric acid: carbonates react to different degrees with hot, partly with cold hydrochloric acid. This property is an important diagnostic criterion for this mineral group.

Odor properties

Flavor characteristics

The distinction of halite and sylvite is traditionally carried out by the fact that the latter has a bitter taste.

Other properties

Radioactivity: This is the property of emitting high-energy radiation, without any energy input. One traditionally distinguishes three types of radiation: alpha, beta and gamma rays. The radiation is measured with a Geiger counter. Radioactivity is potentially harmful even at low doses. Radioactive minerals are uraninite, for example, but also apatite, uranium installs as a trace element instead of phosphorus.
Mobilization: minerals are mobilized by mining, but can also be released by natural processes (erosion ). In the toxicologically relevant heavy metal containing minerals mobilization exceeds by humans by far the natural processes.

Importance

Petrological significance

Each mineral is thermodynamically stable only under certain pressure-temperature conditions. Outside of its stability range, it changes with time in the stable modification to there. Some phase transformations take place abruptly when leaving the stability field ( for example, high - low quartz quartz), others are kinetically inhibited and take millions of years. In part, the activation energy is so high that the thermodynamically unstable modification remains as metastable phase (for example, diamond - graphite). This inhibition of the reaction leads to a " freeze" the thermodynamic equilibrium, that prevailed earlier. Therefore, the mineral composition of a rock provides information on the formation and evolution of a rock and thus contributes to the knowledge of the origin and evolution of the planet Earth at ( see also Präsolares mineral ).

Lagerstättenkundliche importance

Mineral Resources are subdivided into energy commodities, commodities property and element resources. Energy raw materials are, for example, the minerals uraninite and thorite as nuclear fuel. Property resources are used without chemical decomposition in the art, which include, for example, quartz for the glass and clay minerals for the ceramic industry. Element raw materials are mined with the goal of winning a particular chemical element. If it is a metal, it is called an ore Enrichment of raw materials is called a deposit, if it is economically mineable. The term is thus economically, not embossed scientifically: Whether a given occurrence can be commercially exploited depends on the mining and processing costs and the market value of the metal contained from - while the iron content of minerals in up to 50 % must be to a financial to make a profit, filed in 2003, the much more valuable platinum already from a proportion of from 0.00001 % to it. In addition to the breakdown of the use of the polymer also a classification of the origin is common. Sedimentary deposits, such as the banded iron formations formed by precipitation reactions with change of pH, pressure and temperature or by the influence of bacteria or by weathering processes and transport of minerals from their original formation region and its deposition as (soaps), for example of placer gold at the bottom of rivers, lakes or shallow seas. Hydrothermal deposits are formed by surface or deep waters solve certain elements from the surrounding rocks and deposit them elsewhere or from residual fluids after solidification of magma. Magmatic deposits caused by the crystallization of a magma. An example are many platinum and chromite deposits. Metamorphic deposits only arise through the transformation of rocks, such as marble deposits.

Gemmological importance

Some minerals are used as jewelry use. If they are transparent and their hardness is greater than 7, they are called gems, otherwise than gemstones. 95 percent of global sales in this market is achieved with diamonds, the rest almost predominantly with sapphires, emeralds, rubies and tourmalines. To bring the influenced by color and luster beauty of a gemstone to advantage, it must be ground and polished. For this purpose, there are numerous other cuts forms: Transparent or translucent varieties are generally provided with facets sections in which most mutually related fixed angular relationships surfaces, called facets that maximize light reflection. Opaque minerals, however, get smooth, single-surface sections. The Asterismuseffekt a star sapphire for example, can only be achieved through the cabochon. The fire of a cut, brilliant-cut diamonds depends mainly on compliance with certain angular relationships of the individual facets and results from the splitting of white light into the various visible colors ( dispersion).

Other significance

Some minerals are also used as a means of personal care use, such as the clay mineral Lavaerde, which has been used since ancient times as a body and hair cleanser. Other minerals, such as talc, also serve as raw material in the fine arts as well as medicinal purposes ( pleurodesis lubricant in tablet production ).

In many ancient cultures, but also in modern esotericism wrote and writes to certain minerals certain protective and healing effects to. For example, was already in ancient Egypt carnelian due to its color reminiscent of blood as " Stone of Life" and played a relevant role in funeral rituals, as well as protection and Gemstone of the Pharaohs. Also legendary are the alleged protective and healing powers of amber that have already been described by Thales of Miletus and Hildegard of Bingen.

But even without special meaning, a mineral of some importance as a collector's item either in scientific mineral collections to represent the mineral content of a locality (type material ), but also for private hobby collectors who specialize in locality collections or various systematic collections. Due to the rarity of many minerals, which are also often obtained only in very small samples, take private collector specializing in systematic collections of space and cost reasons gladly Micromounts in their collection.

Classification of minerals

See main article Classification of minerals

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