Scoria bricks

 A couple of the scoria brick back alleys in York. These bricks were made from the waste slag produced by the Teeside blast furnaces in the late 19th century. An early example of a recycling solution! They came in either the double hexagon or square and many of them are still a rather lovely shade of blue. Apparently York has around 16 miles of back lanes, a third of which are paved with scoria bricks. They are tougher in withstanding bin lorries and freezing temperatures than paving or tarmac. But sadly alleys have been excavated for utilities and street lighting, and in many cases the scoria bricks have been patched with tarmac, as they are no longer available for replacement.