Melanterite
| Melanterite | |
|---|---|
 |
|
| General and classification | |
| other names |
Iron vitriol |
| chemical formula | Fe [SO 4 ] • 7H 2 O |
|
Mineral class (and possibly department) |
Sulfates (and relatives) |
|
System no. to Strunz and to Dana |
7.CB.35 ( 8th edition : VI / C.06) 06/29/10/01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | P 2 1 / c (No. 14) |
| Lattice parameters |
a = 14.07 Å ; b = 6.50 Å; c = 11.04 Å β = 105.6 ° |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | measured: 1.895 to 1.898; calculated: 1.897 |
| Cleavage | completely after {001}; clearly after {120} |
| Break ; Tenacity | shell-like, brittle |
| colour | light green, greenish blue to bluish green, colorless |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.470 to 1.471 n β = 1.477 to 1.480 n γ = 1.486 |
| Birefringence | δ = 0.016 |
| Optical character | biaxial positive |
| Axis angle | 2V = measured: 86 °; calculated: 80 ° |
| Other properties | |
| Chemical behavior | easily soluble in water |
| Special features | sweet tasting, astringent ( astringent ) |
Melanterite , outdated also known as iron vitriol , is a rather common mineral from the mineral class of " sulfates ( and relatives )". It crystallizes in the monoclinic crystal system with the chemical composition Fe [SO 4 ] · 7H 2 O, so it is a water-containing iron (II) sulfate .
With a Mohs hardness of 2, melanterite is one of the soft minerals that can be scratched with the fingernail , similar to the reference mineral plaster . In nature it is usually found in the form of massive to powdery or fibrous to needle-like mineral aggregates , concretions and stalactites as well as crusty coatings or efflorescence. It seldom forms tabular, prismatic or pseudo- octahedral crystals with shiny glass surfaces.
Etymology and history
Iron vitriol was already known in the Middle Ages and was mixed with various medicinal products and used in impure, copper-containing form as so-called copper water for writing ink.
The mineral was given its name melanterite, which is still valid today, in 1850 from Wilhelm Ritter von Haidinger , who named it after the Greek word μελαντηρία for iron vitriol .
classification
Already in the outdated, but still in use 8th edition of the mineral classification according to Strunz , the melanterite belonged to the mineral class of "sulfates, selenates, tellurates, chromates, molybdates, wolframates" and there to the department "C. Water-containing sulfates without foreign anions ”, where he named the“ Melanterite group ”with the system no. VI / C.06 and the other members Alpersit , Bieberit , Boothit , Mallardit and Zinkmelanterit 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), also classifies melanterite in the category of "sulfates (selenates, etc.) without additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved , so that the mineral is classified in the subdivision “B. With only medium-sized cations "can be found, where it is also named after the" Melanterite group "with the system no. 7.CB.35 and the other members alpersite, bieberite, boothite, mallardite and zinc melanterite.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns melanterite to the class of "sulfates, chromates and molybdates" and there into the category of "water-containing acids and sulfates". Here, too, it is named in the " melanterite group (heptahydrate, monoclinic: P 2 1 / c ) " with the system no. June 29, 2010 and the other members Alpersite, Bieberite, Boothite, Mallardite and zinc melanterite can be found in the subsection of "Hydrous acids and sulphates with AXO 4 × x (H 2 O)".
Crystal structure
Melanterite crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a = 14.07 Å ; b = 6.50 Å; c = 11.04 Å and β = 105.6 ° as well as 4 formula units per unit cell .
properties
When fresh and very pure, melanterite is light blue in color, which takes on a light green color due to partial oxidation in iron (III) sulfate . Depending on the degree of weathering, the mineral occurs naturally in different mixed colors from greenish blue to bluish green. However, its line color is always white.
Melanterite dehydrates in dry air , so it loses part of its crystal water . This process can be intensified by heating until it finally changes into the simply water-containing and yellowish to colorless sulphate mineral Szomolnokit (Fe [SO 4 ] · H 2 O).
Melanterite is easily soluble in water and has a sweet taste, but at the same time has an astringent ( astringent ) effect .
Modifications and varieties
So far, two varieties are known: the copper-containing pisanite and the magnesium-containing kirovite .
Education and Locations
Melanterite is a secondary mineral and is usually formed as an oxidation product from primary iron sulfides such as pyrite , marcasite and pyrrhotite . It is therefore often found as a new formation in ore mines. In rare cases, however, it can also arise directly as a sublimate from volcanic gases .
As a rather rare mineral formation, melanterite can sometimes be abundant at various sites, but overall it is not very common. A total of around 870 sites are known to date (as of 2013).
In Germany, the mineral was found in several places in the Black Forest and in the communities of Nussloch , Bruchsal and Schriesheim in Baden-Württemberg; in the Bavarian Forest , near Lichtenberg and Waldsassen in Bavaria; near Messel , Richelsdorf and in the Taunus in Hesse; on the Rammelsberg in Lower Saxony; in many places and pits in North Rhine-Westphalia such as in the Eifel (up to Rhineland-Palatinate), in the Ruhr area and the Sauerland ; at Königsberg , near Rockenhausen and in the Westerwald in Rhineland-Palatinate; in several places in the community of Nonnweiler and near Dudweiler in Saarbrücken; in the Harz in Saxony-Anhalt; in several places in the Erzgebirge and near Potschappel , in Upper Lusatia and near Oelsnitz in Saxony as well as near Gera , Saalfeld / Saale and Lehesten in Thuringia.
In Austria, the mineral appeared in several places in Carinthia , Salzburg and Styria as well as near Gloggnitz in Lower Austria and in the Tyrolean Inn Valley .
In Switzerland, melanterite was found in the Schaffhausen municipality of Thayngen , in Maderanertal (Golzern) in the canton of Uri, in the salt mine near Bex in the canton of Vaud and in several places in the canton of Valais .
Chvaletice in the Czech Republic, where stalactites of up to 20 cm in length have been discovered, is worth mentioning due to the extraordinary melanterite finds . Even longer stalactites (up to 2 m) and large-scale crusts were found in the " Aljustrel Mine" in Portugal. Particularly beautifully developed crystals of up to 2 cm in size emerged from the mines in the mining town of Bisbee in Arizona and the "Boyd Mine" in Ducktown in Polk County in Tennessee in the USA.
Other localities are in Argentina , Australia , Belgium , Bolivia , Bulgaria , Chile , China , Denmark , France , Greece , Hungary , Iran , Italy , Japan , Canada , Kyrgyzstan , Kosovo , Morocco , Macedonia , Mexico , Namibia , the Netherlands , on New Zealand , Norway , Poland , Portugal , Romania , Russia , Sweden , Slovakia , Slovenia , Spain , South Africa , Taiwan , Turkmenistan , Ukraine , the United Kingdom (Great Britain) and the United States of America (USA).
See also
literature
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 607 (first edition: 1891).
Web links
- Mineral Atlas: Melanterite (Wiki)
Individual evidence
- ↑ a b c d e 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. 383 .
- ↑ Webmineral - Melanterite (English)
- ↑ a b c d Melanterite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 66 kB ]).
- ↑ a b c d Mindat - Melanterite (English)
- ^ 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. 380 .
- ^ A b Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 143 ( Dörfler Natur ).
- ↑ Stalactites made of melanterite, halotrichite and pickeringite from the Algares deposit of the Aljustrel Mine, Beja, Portugal and pit wall encrusted with melanterite from the same site .
- ↑ Find location list for melanterite in the Mineralienatlas and Mindat