High temperature areas in Iceland - Rocks and minerals

Travertine

Travertine (calcium carbonate) - often mixed with silicate sinter - is deposited at high temperature areas, where it sometimes forms whole terraces.

• 
  The Great Geysir and its terrace at Geysir Geothermal Field
• 
  Travertine terrace at Strokkur
• 
  Travertine terraces at Hveravellir
• 
  Details near a hot spring at Hveravellir
• 
  Hveravellir
• 
  Travertine sample

Sulfur

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.

• 
  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
• 
  Sulphur crystalites at a fumarole of the Krafla (volcanic system)
• 
  Mudpots at Námafjall (Hverir), Krafla volcanic system
• 
  Hverarönd, Námafjall
• 
  Sulfur compounds in volcanic gas mixtures cause the bluish colour of the steam.
• 
  Hverarönd
• 
  Mudpots at Seltún,

Iron oxidation

Iron oxidation at volcanoes turns the ground red by hydrothermal alteration.

• 
  Námafjall, Krafla
• 
  Leirgerður, Hveragerði
• 
  Rauðhólar (Jökulsárgljúfur)