High temperature areas in Iceland - Rocks and minerals
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Travertine
[edit]Travertine (calcium carbonate) - often mixed with silicate sinter - is deposited at high temperature areas, where it sometimes forms whole terraces.
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The Great Geysir and its terrace at Geysir Geothermal Field
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Travertine terrace at Strokkur
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Travertine terraces at Hveravellir
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Details near a hot spring at Hveravellir
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Hveravellir
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Travertine sample
Sulfur
[edit]Sulfur is deposited near fumaroles in high-temperature geothermal areas, eg. in Iceland. At some of these, it was mined from the 13th to the 18th centuries.
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At fumaroles, sulfur deposits normally are yellow, whereas in mudpots, they mix with other minerals and the colour often turns to black or a bluish grey
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Sulphur crystalites at a fumarole of the Krafla (volcanic system)
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Mudpots at Námafjall (Hverir), Krafla volcanic system
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Hverarönd, Námafjall
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Sulfur compounds in volcanic gas mixtures cause the bluish colour of the steam.
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Mudpots at Seltún,
Iron oxidation
[edit]Iron oxidation at volcanoes turns the ground red by hydrothermal alteration.
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Námafjall, Krafla
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Leirgerður, Hveragerði
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Rauðhólar (Jökulsárgljúfur)