Green Rust

A rare kind of mineral known as “green rust”, which could be used to scrape toxic metals and radioactive species from the environment, also played a similar and crucial role early in Earth’s history.

Green rust’ was likely widespread in ancient oceans and may have played a vital role in the creation of our early atmosphere. During the Precambrian period, green rust ‘scavenged’ heavy metals such as nickel out of the water

Only discovered last decade, green rust is a highly reactive iron mineral which experts hope could be used to clean up metal pollution and even radioactive waste. This latest discovery proved the effectiveness of green rust as an environmental cleaner.

“Because it is so reactive, green rust has hardly ever been found before in nature and never in a water system like this,”

“The discovery of green rust in Lake Matano, Indonesia, shows for the first time what a key role it played in our ancient oceans — scavenging dissolved nickel, a key micronutrient for methanogenesis.”

Iron(II) hydroxide or ferrous hydroxide is a compound produced when iron(II) ions, from a compound such as iron(II) sulfate, react with hydroxide ions. Iron(II) hydroxide itself is practically white, but even traces of oxygen impart it with a greenish tinge. If the solution was not deoxygenated and the iron reduced, the precipitate can vary in color starting from green to reddish brown depending on the iron(III) content. This precipitate is also known as "green rust" in the crystal lattice of which iron(II) ions are easily substituted by iron(III) ions produced by its progressive oxidation. In the presence of oxygen the color changes quickly. Green rust is a powerful reducing agent and also a layer double hydroxide (LDH) capable to sorb anions because of the presence of positive electrical charges borne on its surface.

More information

In the ancient oceans, green rust's ability to pull nickel out of the water would have been critical for some life forms, since nickel is an important nutrient for microbes that produce methane. Methane reacts with oxygen to produce carbon dioxide, so less nickel means less methane, which would mean oxygen could remain in the atmosphere and accumulate over time/

The research has other implications for understanding the composition of ancient oceans. To understand the nutrient composition of the ancient oceans, it's important to know which iron minerals were around at the time. Iron minerals take up dissolved nutrients and carry them to the seafloor, where they eventually become preserved in rock. But because different iron minerals behave differently, scientists must know what iron minerals were present