The copper ore occurs in the form of malachite, which stains the rock green.
Hard volcanic stones from the beach were used as hammers to break off the rock. Over 2.500 have been discovered in the tunnels and most are now in the archaeology store. Many of these have broken ends, indicating hard use. Animal bones were then used to scrape out the ore. Many of these have been stained green by the copper.
In places where the rock was too hard to break with the hammerstones, it was weakened first by fire. A small fire was lit against the rock. As the heated rock cools, it contracts and fractures, making it easier to remove. The high temperatures redden the rock and traces of charcoal have been found around the site.
Candles made from animal fat were the only source of light. Some of the tunnels were so small they could only have been worked by children.
Ore bearing rock was sorted roughly underground and waste rock packed into abandoned workings.
On the surface, the ore was crushed in a pestle and mortar, separating the ore from the waste rock. It may have been sorted further by hand or by water, as there is a natural spring close to the mine site.
Smelting was done in small kilns on the surface. These were fuelled by charcoal which burns hotter than wood. As copper is a fairly soft metal, about 10% of tin from Cornwall was added to make bronze. This was a harder and more practical. Molten bronze was poured into moulds to make tools, weapons and jewellery.
There is a replica of metal working shelter above the open cast mine, showing some of the equipment used.
Nothing was wasted and there is evidence of bronze scrap which would have been melted down to form new tools.
It has been estimated that 1,800 tonnes of copper ore were removed from the mines in the Bronze Age. It is not known how many people worked in the mine or associated industries and no settlement has been found around the mine site yet. It is thought to be hidden by the C19th spoil tips. Evidence of human bones have been found.
