Calcite Garnet Pyrite Pyroxene Skarn, Proterozoic, Grenville Tectonic Province, Marmora, Ontario.
"Skarns are formed at the contact zone between intrusions of granitic magma bodies and carbonate sedimentary rocks such as limestone and dolostone. Hot waters derived from the granitic magma are rich in silica, iron, aluminium, and magnesium. These fluids mix in the contact zone, dissolve calcium-rich carbonate rocks, and convert the host carbonate rock to skarn deposits in a metamorphic process called metasomatism. The resulting metamorphic rock may consist of a very wide variety of minerals dependent largely on the original composition of the magmatic fluids and the purity of the carbonate sedimentary rocks." -DESCRIPTION COURTESY OF WIKIPEDIA
This rock is composed of andradite garnet, calcite and pyrite. The layers of garnet open out into eye-shaped blobs called "augen", the German name for eye. Marmoraton Mine ore deposit was found in the 1950s using airborne geophysics. This deposit held a rich source of iron. The iron was first detected by Canada’s first geologist William Logan when it attracted his compass needle while surveying the area. An airborne magnetic survey was done and Bethlehem Steel Corporation opened Marmoraton Mine in 1955. Mining continued until 1977. The mine shipped iron ore pellets to Bethlehem Steel Mills in Buffalo, New York.
More information about the Marmoraton Open Pit Iron Mine, Marmora, Ontario.