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Earth Treasures

Earth TreasuresIn the 18th and 19th centuries Cornwall was one of the richest mining economies in the world. Industries, inventions and communities were built on its wealth of underground treasures. But why were the metals and minerals so valuable and what were they used for? And how have they changed the way we live today?


Initially used as coinage, copper was also used to sheath and protect the hulls of British ships; as a building material, in the manufacture of bronze and brass, and for machine bearings and fittings. Copper also became essential in the electrical and communications industries thanks to its excellent electrical conductivity and low reactivity.

Your fridge, microwave, washing machine, television, DVD player and computer all depend on copper to work.


It’s thought that Cornish tin has been traded throughout Britain and Europe for around 4,000 years. Alloyed with copper to make bronze for implements and weapons, it was of huge strategic importance to rulers and traders for centuries. Tin was also used to make pewter dishes and ornaments, and for bells, organ pipes, toys and whistles, and building. Tin revolutionised the food industry as tin-plated iron, and then steel, cans enabled food to be preserved and transported. There’s even a small amount of tin in toothpaste to help prevent tooth decay.


With a reputation as the poison of choice for fictional villains, arsenic was originally a by-product of copper and tin processing.  It was used for dyes and pigments in the Lancashire cotton industry and later became a popular insecticide. It is known for being highly poisonous and deadly; however some of its compounds have been found to have medicinal uses. Alloyed in very small amounts with other metals it is used in the manufacture of car batteries, lead shots and bullets, and laser diodes for Blu-ray technology, bar code scanners and laser printers.

Arsenic is known for being deadly but some of its compounds have medicinal uses.


Very soft, easy to mould, a relatively poor conductor of electricity and resistant to corrosion, lead has been used for thousands of years for construction, pipes, and weights and balances. It is also used to make munitions and a large proportion of the world’s lead production is for car batteries. It used to be common in paint pigments and pesticides but this was phased out as lead is now known to be poisonous to humans and animals, causing damage to the nervous system and blood and brain disorders. It does have a use in hospitals though, shielding staff from radiation in x-ray rooms.


Today, we may think of zinc as just one of the many vitamin and mineral supplements on offer in the pharmacy, but this robust, dense metal crops up all over the place. When alloyed with copper it forms brass, making a stronger, more pliable, and corrosion resistant metal. It is commonly used to galvanize (protect against corrosion) iron and steel. It is used for coins, glue, rubber, paint and glazes. You may even rely on zinc when you’re sunning yourself on the beach as zinc oxide is often used as an ingredient in sun blocks.


It is very likely that you carry silver with you wherever you go, and not just if you’re wearing a necklace or ring made from the precious metal. Silver has the highest electrical conductivity of any element so is very useful in the production of electronic circuits and chips. Your mobile phone, MP3 player, laptop and digital camera all rely on small amounts of silver to work. Silver has traditionally been used for coinage, jewellery, ornaments and tableware, but it is also used for medical equipment (it is sterile), batteries and photography.