Siderite
| Siderite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | Fe [CO 3 ] |
|
Mineral class (and possibly department) |
Carbonates (and relatives, see classification ) |
|
System no. to Strunz and to Dana |
5.AB.05 ( 8th edition : V / B.02) 01/14/01/03 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-scalenohedral; 3 2 / m |
| Space group | R 3 c (No. 167) |
| Lattice parameters | a = 4.69 Å ; c = 15.38 Å |
| Formula units | Z = 6 |
| Physical Properties | |
| Mohs hardness | 4 to 4.5 |
| Density (g / cm 3 ) | 3.7 to 3.9 |
| Cleavage | completely according to {10 1 1} |
| Break ; Tenacity | uneven to scalloped |
| colour | yellow, brown, black |
| Line color | White yellow |
| transparency | transparent to translucent |
| shine | Glass gloss to pearlescent gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.875 n ε = 1.633 |
| Birefringence | δ = 0.242 |
| Optical character | uniaxial negative |
Siderite , also known under the mining names Eisenkalk , Eisenspat , Spateisenstein , Chalybit and Stahlstein or under its chemical name iron carbonate or iron (II) carbonate , is a frequently occurring mineral from the mineral class " carbonates and nitrates " (formerly carbonates, nitrates and borates). It crystallizes in the trigonal crystal system with the chemical composition Fe [CO 3 ] and develops mostly late or coarse masses or fine-grained, dense, spherical and grape-shaped aggregates, also called spherosiderite . Rhombohedral crystals with sometimes curved surfaces are rather rare .
Siderite is usually pale yellow to brown in color. Manganese-rich varieties are more likely to appear black. The crystals are transparent to translucent and shine like glass to mother-of-pearl. The very good cleavage after the rhombohedral surfaces is remarkable.
Etymology and history
The mineral received its name in 1832 from François Sulpice Beudant , who referred to its composition as "siderose", after σίδηρος sideros , the Greek word for iron . Siderit was first scientifically described in 1845 by Wilhelm Ritter von Haidinger .
As one of the most important iron ores , siderite has been known since prehistoric times . With its processing, the Iron Age began in various cultures at different times .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the siderite belonged to the mineral class of "carbonates, nitrates and borates " and there to the department of "anhydrous carbonates without foreign anions ", where it belongs together with calcite , gaspéit , magnesite , Otavite , rhodochrosite , smithsonite , spherocobaltite and vaterite the "calcite group" with the system no. V / B.02 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns siderite to the class of "carbonates and nitrates" (the borates form a separate class here) and there into the department of " Carbonates without additional anions; without H 2 O “. However, this section is further subdivided according to the type of cations involved , so that the mineral can be found according to its composition in the sub-section "alkaline earth (and other M 2+ ) carbonates", where it is found together with calcite, gaspéit, magnesite, otavite , Rhodochrosite, smithsonite and spherocobaltite the "calcite group" with the system no. 5.AB.05 forms.
The systematics of minerals according to Dana , like the outdated 8th edition of Strunz's systematics , assigns the siderite to the common class of "carbonates, nitrates and borates" and there in the department of "anhydrous carbonates". Here it is together with calcite, magnesite, rhodochrosite, spherocobaltite, smithsonite, otavite and gaspéit in the "Calcite group (Trigonal: R-3c)" with the system no. 01/14/01 to be found in the subsection of " Anhydrous carbonates with simple formula A + CO 3 ".
Crystal structure
Siderite crystallizes trigonal in the space group R 3 c (space group no. 167) with the lattice parameters a = 4.69 Å and c = 15.38 Å as well as 6 formula units per unit cell .
properties
Siderite is only soluble in hydrochloric acid after heating, whereby it foams up with the formation of carbon dioxide (CO 2 ). It differs from calcite ( calcite ), which reacts violently with cold, dilute hydrochloric acid, foaming and forming CO 2 .
Modifications and varieties
Oligonite is a manganese-containing and pistomesite is a magnesium-containing variety of siderite.
Education and Locations
Siderite can be found in a number of rock types - it forms diagenetically in clayey sediments in the form of so-called clay iron concretions and metasomatically in carbonate sediments, which can lead to minable deposits by today's standards. The mineral can also be found in hydrothermal veins that were formed at medium to low temperatures. In addition, siderite occurs in various metamorphic and igneous rocks.
The ore mountain in Styria ( Austria ) is the largest siderite deposit in the world with around 400 million tons of minable ore. So far (until 2010) around 250 million tons of it have been mined. The current annual production from the largest open-cast ore mine in Western Europe is around 2 million tons of fine ore (corresponding to 6.5 million tons of rock).
Other significant but already largely mined deposits of siderite in Austria can be found in Radmer in Styria (underground mining 1939 to 1979 with around 450,000 tons annually at last) and on the Hüttenberger Erzberg in Carinthia (mining from around 300 BC to 1978 , last about 200,000 tons annually in underground mining, peak in 1940 with 313,000 tons). In Germany there are considerable siderite deposits in the Siegerland (Westphalia), in the Westerwald , in the Harz (Neudorf), in the Thuringian Forest (Schmalkalden, Kamsdorf) and in the Saxon Ore Mountains . On the Saar, it was promoted in the form of Lebacher eggs .
Large siderite deposits can also be found in Australia , Bohemia (Czech Republic), Bolivia , Minas Gerais (Brazil), China , Portugal (Panasqueiro), Spain and England (Tavistock in Devonshire and Camborne Redruth in Cornwall). Are famous, the spectacular-looking spätigen masses in Mont Saint-Hilaire in Quebec ( Canada have been discovered).
Altogether, Siderite has so far (as of 2011) been found at around 4700 sites, including rock samples from the Mid-Atlantic Ridge and the Chinese Sea (Qiongdongnan Basin).
use
With almost 50% iron content and because of its ease of smelting, siderite is a valuable iron ore .
Siderite is too soft and sensitive to use as a gemstone . Clear and visually appealing varieties are occasionally offered to collectors in various smooth or facet cuts.
See also
literature
- Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th fully revised and updated edition. Springer Verlag, Berlin et al. 2005, ISBN 3-540-23812-3 , pp. 64 .
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Dörfler Verlag GmbH, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 114 .
Web links
- Mineralienatlas: Siderit , Mineralienatlas: Mineralienportrait / Siderit (Wiki)
- Webmineral - Siderite (English)
Individual evidence
- ^ A b c 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 , p. 286 .
- ↑ a b c Siderite at mindat.org (English)
- ↑ Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 978-3-921656-70-9 , p. 191 .
- ↑ Christian Treml: Erzberg: 250 millionth ton of ore mined. (PDF; 40 kB) VA Erzberg GmbH, May 11, 2010, accessed on May 13, 2010 .
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 222 .
- ↑ realgems.org - Siderite (with images of various rough and precious stones)