Mining in Cornwall and Devon is when people dig deep underground to take out metals and minerals like tin, copper, and lead from the Earth.
This was very important a long, long time ago when there were no machines or factories, and things were made by hand. The metals and minerals that were taken out of the ground were used to make tools, weapons, and things to trade with other countries.
The people who did the mining were called miners. They had to work very hard and in very dangerous conditions because the mines were dark, hot, and sometimes flooded with water.
The miners used tools like pickaxes, shovels, and drills to break the rocks and bring out the metals and minerals. They would then take the rocks to a special place where they crushed them and separated the useful bits from the not-so-useful bits.
Mining was very important to Cornwall and Devon, but now there are not as many mines as there used to be because machines can do most of the work. However, some people still mine in Cornwall and Devon for things like china clay, which is used to make things like plates and toilets!