BIFIn our last post (see tinyurl.com/nmynqyo) we discussed evidence of an early whiff of oxyg
BIFIn our last post (see http://tinyurl.com/nmynqyo) we discussed evidence of an early whiff of oxygen in a 2.98 billion year old soil as an early prelude to the great oxygenation event 2.6 billion years ago. When the latter event happened, the oxygen oxidised iron dissolved in the oceans and sank to the bottom alongside layers of silica. The resulting rocks are known as banded iron formations, and are our main source of iron, as they contain easily mined high concentrations of the metal. Here is a lovely specimen, with tiger eye chalcedony in between the red iron rich layers. LozImage credit: Maitri -- source link
#geology#chalcedony#chemistry#silica#chert#tiger eye