Unique Proterozoic Banded Iron Stromatolite from Minnesota
- Banded Iron Deposit with Hydrothermal Silkstone Intrusion
Time: Early Proterozoic, ~ 2.0 to 2.2 Billion Years Old
fossil is 130 mm by 110 (maximum)
Merritt #2 Mine, Cayuna North Range, Crow Wing County Minnesota
This banded iron is metasediment (sediment that has undergone metamorphism)
and has a high content of magnetite (Fe3O4). Minute crystalline
forms of other mineral-based compounds are also present; Whether
the sediment was of bioorganic origin (stromatolite) is indeterminable,
but likely. This one shows an unusual association of Silkstone (also
known as Minnesota Tiger Eye) with the banded iron formation. Note
the distortion of the bands near the wall of the intrusion. This
material is the result of hydrothermal activity which is typically
accompanied by various extremophilic organisms, making for a most
unique duality of biogenic sources. In the 80 years of operation
from 1904 over 100 million tons of iron ore was recovered from the
Cuyuna Iron Range, much of which had measurable quantities of Manganese.
See my other offerings for an example showing the pink Manganese-rich
specimen has been hand-polished to a glassine finish on one side
with fine carbide and diamond abrasive, a very labor-intensive job.
It comes from a 30-year-old deposit which is no longer available.
The contrasting coloration seen here is most striking.
have persisted to the modern day in such places as Shark Bay, Australia
where they continue their billions of years old lifestyle. While
this piece would make a fine present for any natural history buff,
anyone who appreciates art would also be glad to get thus wonderful
specimen as a gift.
click stromatolites pictures