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THIS OBJECT IS PART OF THE PROJECT 'A HISTORY OF CORNWALL IN 100 OBJECTS'.

HAYLE ARCHIVE. Many people visiting the older parts of Copperhouse will have noticed the heavy black building blocks peculiar to this area. These brick-shaped building blocks are known as Copperhouse slag or scoria blocks. This is a typical example.

They were cast from the residue of the copper smelting works that operated at Ventonleague 250 years ago. The Copperhouse Foundry operated from 1750 to c.1820, and thereafter most of Cornwall's copper ore went to Wales, where the coal supplies were, for smelting. The copper was smelted in reverberatory furnaces, a process which involved eight roastings and meltings of the ore. The slag or scoria from the first melting only was used for making building blocks, the residues from subsequent meltings being so rich that they were re-cycled through the furnaces again.