Banded Iron Formation (BIF)

I was recently reminded of how beautiful Banded Iron Formations (BIFs) are and so thought I'd write about them today. The photo on the left is of the BIF that I have displayed on my mantle and specifically is known as a Tiger-eye BIF. It makes lovely jewelery as well as display pieces.

One thing about BIFs is that it is very old. They are some of the oldest sedimentary rocks known and date to as old as 3 billion years old. Earth's conditions were very unique back then and it has not been the same since so the rock is really unusual. BIFs are thought to have formed from the oxygen that was released from ancient photosynthetic bacteria (bluegreen algae) combining with dissolved iron in the Earth's oceans and precipitating out onto the muddy ocean floor. Since this was a seasonal process, you got alternating bands of iron oxide and shale rock. You can also get bands of jasper or tiger eye (a type of quartz). In massive form, BIF is unremarkable except that it is extremely heavy because of the iron content. When polished, BIF can be very beautiful. The red jasper or tiger eye looks great layered with the silvery hematite or magnetite.