Paleoproterozoic Tiger Iron Stromatolite
Banded Iron Deposit
Time: Paleoproterozoic (1.8 Billion Years Old)
mm by 145 mm
Ord Ranges, Pilbara, Western Australia
A polished section of what is termed locally “Tiger Iron”.
Known as Jaspelite, it is a banded structure of Tiger Eye, Red
Jasper, and Hematite. Stromatolites are remnants of the most ancient
of colonial organisms. Stromatolites are fossils that are the result
of the work of simple blue-green “algae” or Cyanophytes,
which lived in chains or mats covered in a jellylike substance.
By taking in carbon dioxide as a food source, the precipitate limy
deposits on the jelly that builds up in layers. Thus these organisms
build up stony supports for their colonies. These mound like structures
can be anywhere from several centimeters to several meters in height.
The production of oxygen is thought to have led to the “rusting
of the seas” which brought about deposition of extensive
iron deposits such as the Mesabi Range. Hematite is an iron mineral,
and is one of the components of this banded structure (dark bands).
Stromatolites have persisted to the modern day in such places as
Shark Bay, Australia where they continue their billions of years
old lifestyle. This one is quite natural in appearance on all but
the surface which has been given a high polish to show off the
myriad of colors.