Pyrite vein in iron-formation in the Archean of Ontario, Canada.

This is the Sir James Mine, also known as the Sir James Pit. It is an inactive iron mine near Wawa, Ontario, Canada.

Dark brown-weathering rocks are abundant at the site. The rocks are heavy to very heavy for their size. The dominant lithologies appear to be quartzite, iron-formation, and black smoker rocks. The iron-formation rocks have siderite and hematite. Pyrite masses, pyrite veins, and disseminated pyrite are common. Much of the iron-formation is metamorphism-recrystallized siderite iron-formation. Coarsely-crystalline siderite in some samples has lustrous, almost metallic-lustered, cleavage planes. Large, weathered siderite rhombs are present. Fine-grained, brown-and-gray, banded rocks here appear to be hematite-quartz iron-formation - the brown layers streak red (= massive hematite). The siderite iron-formation here was deposited on the seafloor next to black smoker vents, which were the source of the siderite - this is a SEDEX deposit (= sedimentary exhalative).

Seen here is a crack-exposed pyrite vein in an iron formation sample. Pyrite, also known as "fool's gold", is iron sulfide - FeS2.

Stratigraphy: Helen Iron-Formation, Michipicoten Group, Neoarchean, 2.696 to 2.749 Ga