Bog iron

As a bog iron or bog iron ore are known in extant and fossil groundwater soils by particularly high levels of iron solidification marked, occurring rock- boulder -like as concretions or bank- like as soil horizons.

• 4.1 iron extraction
• 4.2 Building material

Basics

In bog iron is solidified by iron minerals sediment fractions of the soil. In most cases, these are sand, clay and silt, sometimes gravel, and sometimes organic substrates (especially peat ) with high metal contents.

Main mineral is limonite - - These often up to half a meter thick horizons of the iron contents may well be up to 45 percent. In many of these enrichments downstream play manganese, partially phosphorus and other elements play a role.

Bog iron can be smelted regardless of its average rather low iron contents like any other iron ore to iron production.

Designations

The term bog iron is because of this close is present in groundwater - soil under the Rasensode and can easily be recovered " with spade and hoe ". Other names for the sometimes appearing as slag, red-brown to ( at higher manganese contents ) blue black work hardening are limonite, bog iron stone, swamp bog iron or simply Rasenerz or bog.

Bog iron should not be confused with its main mineral constituent of limonite, which is also referred to as limonite or ore. More possibilities for confusion conceptual kind exist with the sound or siderite -called iron mineral siderite, with the rock iron sandstone, the hardpan or Orterde of podzols and with bean ore. As a bog iron earth largely unconsolidated accumulations in Gleyböden be called, which can be a precursor to the development of Eisenstein's lawn.

Formation

Bog iron can occur in different ways. Essential are always redox processes, partly with the participation of microorganisms ( bacteria, for example Acidithiobacillus ferrooxidans ). In the range of fluctuation of the groundwater, dissolved in the iron and manganese salts ( leachate here plays only a minor role ), fall upon contact with oxygen oxide / hydroxidic iron and manganese compounds from. Pronounced bog iron formations often go to small fluctuations of the water table at the same time high iron water back. The emergence period of bog iron extends, depending on the occurrence usually have hundreds to thousands of years.

Particularly common is bog iron forms in the oxidation horizon Go by gleys. According to the pedological Mapping Go- horizons present as bog iron concretion limonite as Gkso and those with gebanktem bog iron are called GMSO. From a certain thickness and the typical fixed expression these horizons are also called short RES. In Gleypodsolen and Anmoorböden can also form bog iron.

In Northern Germany arose during the Holocene, after the last ice age, veritable bog iron ore deposits. They formed mainly in floodplains in flow through iron-bearing groundwater fine to medium -grained sands. This wurzelundurchlässigen from the bog iron soils are limited as agronomically useful and can be used as a rule only as a meadow or pasture.

During the cold periods of the formation of bog iron in the water-bearing warmer interstadials is possible. For example, run the gravel body of the Rhine terraces on the lower middle Rhine manga very rich bog iron horizons. These are often linked to powerful cross-bedding body. These concretions indicate fossil, so earlier groundwater levels and are therefore distributed over the whole profile and not only found near the ground level.

Occurrence and Protection

Bog iron is used worldwide, especially in the temperate latitudes, especially in humid and swampy lowlands, before. Climate and landscape -related concerns, this primarily in Europe, the northern central and southern Northern Europe. A through the center of Schleswig-Holstein running from Hamburg to Flensburg strip extensive occurrence is investigated archaeologically.

There are recent, today still located near the earth's surface, as well as fossil, buried by further soil or rock layers over time or covered deposits. Commonly treated only the latter in the geological literature.

Former major central European deposits are largely considered dismantled. Mostly randliche residues or small powerful or small-scale sites in the old deposits are only present that are not commercially recoverable. Deposits with usable as a building material larger chunks, which are required, for example for the repair of historic and listed buildings standing from bog iron, have become rare.

Some bog iron - residual populations and lowland soils with current iron oxide precipitation are in Germany now - as the successor of the Federal Soil Protection Act - because of its rarity and its natural, cultural and historically significant archival function as " priority areas for soil protection " planning law fixed, usually at the local level.

Place and field names

The occurrence and the use of bog iron were - similar to the iron ore - directly its name to numerous locations and field names, in particular with the part of the name - iron in Germany, among others, for Isernhagen and Iserbrook ( Isern = iron ), iron Hausen, Eisemroth (both in Mittelhessen ) and Jerrishoe (Danish jern = iron), as well as several places called component - huts ( from smelting ). In East Germany, where many place and field names are of Slavic origin, is equivalent to the syllable - Rud (eg Berlin- Rudow ).

Use

Iron extraction

Bog iron with iron concentrations of about 20-40 % has been obtained since the Iron Age in Central and Northern Europe as iron ore and smelted in Rennöfen.

In the 19th century the local bog iron deposits were used for iron production in the absence of other sources on the Lower Rhine.

The heavy industry in the Ruhr region last used in World War II regional bog iron deposits of the Emscher valley as a substitute for the richer ores normally used. In Eastern Europe and some other parts of the world bog iron is mined today.

Building materials

The well- editable bog iron was used as a building material. However, to be suitable only particularly metal-rich "stones", as material is relatively soft with low iron levels and has a very low resistance to weathering. Iron -rich, hard and good heat-insulating through its pores bog iron was predominantly used in the rock- poor lowland regions of Central Europe for the construction of walls, foundations and buildings.

Thus, for example, the city walls of the Brandenburg town of Dahme mainly of bog iron and is therefore called " Iron Wall ". In parts of Mecklenburg-Vorpommern are old houses ( Klump houses) and churches that there bog iron -called "nugget " was built entirely from the typical; inter alia, the stud Redefin and various houses in the southwestern Mecklenburg as in Wöbbelin or Grebs - Niendorf. The Ludwigsluster city wall consists of this material, as well as the pylon -like bell towers of the town church. The towers of the Evangelical Lutheran Churches of St. Nicolai (Hannover -Both field) and in Winsen (Aller) on the southern edge of the Lüneburg Heath have also been built from bog iron.

Bog iron was used because of its rustic structure in some engineering structures of Dessau- Wörlitz, especially in Woerlitzer Park. Particularly noteworthy is named after the name of the typical landscape lawn Eisenstein's " Eisenhardt " assembly. The so-called "stone", a miniature replica of Mount Vesuvius as well as bridges and tunnels systems in the park were built for the sake of the effect with bog iron. Outside of the park is the " Rough guard house " to call on the lilac wall between Vockerode and Wörlitz. In the designed partly by Woerlitzer model New Garden Potsdam façade cladding the shell grotto consists partly of bog iron.

Furthermore, bog iron is used occasionally in the visual arts as a natural means of design.