Goethite (FeO(OH); /ˈɡɜːrtaɪt/[5]) is an iron-bearing hydroxide mineral of the diaspore group. It is found in soil and other low-temperature environments. Goethite has been well known since ancient times for its use as a pigment (brown ochre).
Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. It was first described in 1806 based on samples found in the Hollertszug Mine in Herdorf, Germany.
The mineral was named after the German polymath and poet Johann Wolfgang von Goethe (1749–1832).
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"Streams carry dissolved iron from nearby mountains.
In the bog, the iron is concentrated by two processes.
The bog environment is acidic, with a low concentration of dissolved oxygen.
In the acidic environment of the bog, a chemical reaction forms
insoluble iron compounds which precipitate out.
But more importantly, anaerobic bacteria
(Gallionella and Leptothrix) growing under the surface
of the bog concentrate the iron as part of their life processes.
......Their presence can be detected on the surface
by the iridescent oily film they leave on the water ...
another sure sign of bog iron.
In Iceland, the film is called jarnbrák (iron slick).
When a layer of peat in the bog is cut and pulled back using turf knives,
pea sized nodules of bog iron can be found and harvested.
Although the iron nodules are reasonably pure,
there aren't many of them.
They are, however, a renewable resource.
About once each generation, the same bog can be re-harvested
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https://en.wikipedia.org/wiki/Bog_iron
Around the year 1100, the area where Gouda now is located was swampy and covered with a peat forest, crossed by small creeks such as the Gouwe.
Along the shores of this stream near the current market and city hall, peat harvesting began in the 11th and 12th centuries. In 1139, the name Gouda is first mentioned in a statement from the Bishop of Utrecht.
