F is for the Forgotten Facade of a Furnace -- a 110+ year old steam boiler, to be specific! This F comes to you from the corner of the old Quincy Mine #7 boiler house, built in 1898.
The darker rock is poor rock from the mine -- mineral-free rock brought up from the mines and reused in buildings. Many Copper Country mine buildings -- especially from before 1900 -- have poor rock foundations. The red quoins are made of Jacobsville Sandstone, a building material native to the Keweenaw (and very commonly used in buildings up here). They sure don't make 'em like they used to!
While I'm at it -- does anyone else think that the lines, stripes, and swirls in the sandstone look a bit like close-ups of Jupiter?