August 1996

The Sherman Mine in Temagami, Ontario, 800 kilometers north of Toronto, was the source of a multi-ton boulder of banded iron formation. This 2.2 billion year old formation consists of thin layers of sediments that were deposited in a marine environment and subsequently metamorphosed. Its mineralogy records a time in the early Earth's history when the atmosphere and oceans contained significantly less oxygen then their present-day counterparts.

Dr. Ro Kinzler, seven months pregnant, choosing a sample of banded iron formation at the now defunct Sherman Mine.

photo credit: Margaret Carruthers, © American Museum of Natural History