Ohmoto and his team believe that this specific layer of hematite formed when a plume of heated water, like those found today at hydrothermal vents, converted the iron compounds
into hematite using oxygen dissolved in the deep ocean water.
So far, these iron compounds
require temperatures too chilly for liquid nitrogen.
Black powder mainly consists of iron compounds
such as magnetite (mill scale) and iron sulfide and includes sand and clay, salt, weld spatter and even metallic iron.
New mystery materials: In 2008, researchers created a stir by discovering a whole second family of high-temperature superconductors, consisting of iron compounds
instead of copper-and-oxygen-compounds.
The delicately hued type of natural quartz known as amethyst, for example, owes its distinctive purple color to traces of iron compounds
that are locked into its crystal lattice as it grows.
Among these minerals, Raiswell's research shows, are iron compounds
that can fertilise large-scale growth of photosynthetic plankton, which take in carbon dioxide from the air as they flourish.
When plants in poor soil get low on iron, a protein in the roots of many species helps them take in oxidized iron compounds
that are normally unusable.
That membrane probably contains a protein that lures iron compounds
out of solution and concentrates them inside the membrane.