Systematics of the minerals

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The mineral system is a list of all known mineral types sorted by chemical composition and crystal structure .

In mineralogy , a distinction is made between two basic systematics: The systematics according to Hugo Strunz , which is mainly used in German-speaking countries, and the systematics according to James Dwight Dana used in the English-speaking world, especially in the United States . On the surface, both systematics look very similar, as their first, rough classification , the so-called “mineral class”, follows the chemical composition in both systems.

Depending on the version of the system, the number of mineral classes in this first classification varies between eight and ten.

In the further subdivisions, the old systematics of minerals according to Strunz (8th edition) and the new systematics of minerals according to Strunz (9th edition) (since 2001) are initially based on the chemical composition, while the systematics of minerals according to Dana the Prefers crystal structure as a distinguishing feature. Therefore, among other things, quartz is assigned to the oxides in Strunz's system due to the compound SiO 2 . Its crystalline structure of interconnected SiO 4 tetrahedra corresponds to that of silicates, among which it can also be found according to Dana's systematics.

Mineral classes

I elements

In this mineral class are all solid , occurring so in nature in elemental form chemical elements gathered. These include 33 elements, some of which can exist in several modifications in a stable or metastable manner on the earth's surface, such as carbon in the form of diamond , graphite , chaoite and fullerite . The class of elements also includes natural alloys , intermetallic compounds , carbides and their relatives. These minerals are rare, but some of them have a certain economic importance. A total of around 150 types of mineral belong to the class of elements.

II sulfides, sulfosalts and related compounds

The class of sulfides and sulfosalts includes all compounds between metals and the chalcogens sulfur , selenium , tellurium (Te), arsenic , antimony and bismuth (Bi, formerly bismuth), i.e. selenides , tellurides , arsenides , antimonides , bismuthides , sulfarsenides , sulfantimonyides and sulfbismutides . These include around 750 minerals. Most metals (especially non-ferrous metals ) are extracted from sulphidic ores.

III halides

The currently around 230 halides consist of a compound with the halogens fluorine , chlorine , bromine or iodine with cations such as sodium or calcium . The representatives of these minerals occur in salt deposits .

IV Oxides and Hydroxides

The combination of metals or non-metals with oxygen or hydroxyl groups (OH - groups) gives rise to oxides or hydroxides (earlier notation oxides or hydroxides). While hydroxides are formed as so-called secondary minerals on the earth's surface, oxides are formed under high pressure in the earth's interior.

Together with the related compounds of arsenites , antimonites , bismuthites , sulfites , selenites , tellurites , iodates and the V [5,6] vanadates as well as the uranyl hydroxides , around 750 minerals belong to this class.

V carbonates and nitrates

The class of carbonates (outdated: carbonates ) and nitrates include the salts of nitric acid and carbonic acid . Among the uranyl compounds , the uranyl carbonates also belong to this class.

As the main constituent of limestones, carbonates are widely used, while nitrates only occur in a few salt lakes in the tropics . A total of around 260 minerals are carbonates and nitrates.

VI borates

Borates are the salts of various boric acids . For structural reasons, the variety of borates is even greater than that of silicates. The roughly known 160 borate minerals are divided into five (island, group, chain, layer and framework borates) or eight (mono-, di-, tri-, tetra-, penta-, hexa-, hepta), depending on the type of system - and other megaborates as well as unclassified borates) subclasses differentiated. Borates are rare minerals that can only be found in salt lakes.

VII Sulphates, Selenates, Tellurates, Chromates, Molybdates and Wolframates

To the class of sulfates , selenates , tellurates , chromates , molybdates and tungstates include the salts of sulfuric acid , chromic acid , molybdic acid and tungstic acid , in addition, the selenates, and tellurates with divalent tetrahedral complex ions (Ex. [SO 4 ] 2- ), and the Uranylsulfate , Uranylmolybdate , Uranyl tungstates and thiosulfates . The group includes around 450 minerals. While sulphates are of great importance in sedimentary rocks and tungstates can occur to an economically relevant extent in hydrothermal deposits, the other subgroups are very rare.

VIII Phosphates, Arsenates and Vanadates

The currently around 980 phosphates , arsenates and vanadates include all minerals with the acid residue H 3 XO 4 , where X stands for phosphorus , vanadium , arsenic . In addition, the uranyl phosphates and uranyl arsenates belong to this class. The only rock-forming mineral of this group is apatite, other minerals always occur only in small quantities.

IX Silicates and Germanates

The silicates with its many rock-forming minerals are the largest class (including quartz about 90% of the Earth's crust) is where the [SiO 4 ] 4- - tetrahedron is an essential element. The very rare Germanates are also included .

X Organic minerals

These include salts of organic acids such as the acetates , oxalates , benzene salts and cyanates as well as aliphatic and aromatic hydrocarbons , nitrogen-containing compounds ( amides of organic acids or heterocycles ) and resins . The around 70 known organic minerals are of only very minor importance both geoscientifically and economically and are predominantly formed in the vicinity of fossil fuel deposits.

Amber is not recognized by the IMA as an independent mineral, but is still listed in the mineral systematics as the namesake of a mineral group within the department of " various organic minerals " (formerly the " resin-like compounds ").

See also

literature

  • Karl Hugo Strunz , Christel Tennyson : Mineralogical tables . 8th edition. Academic publishing company Geest & Portig KG, Leipzig 1982.
  • Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X .
  • Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 .

Web links

Individual evidence

  1. ↑ a b c d e f g h i Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  2. ↑ Martin Okrusch, Siegfried Matthes: Mineralogie. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 79 .