Processing and the Mill

processing machinery in the Mill

When the tin ore was found underground, it did not occur in big pieces, but in small crystals scattered through the rock.

Once the rock has been mined underground it was hoisted to the surface where it needed to be processed to become a tin concentrate – a fine powder know as ‘black tin’. This would be taken away to be smelted into the tin metal that we are familiar with.

The tin bearing rock that had been hoisted to the surface was then put through the dressing process so tin ore could be ‘processed’ to a fine powder known as black tin or tin concentrate. 

At Geevor, only about 1% of the rock recovered was tin ore - smaller quantities of other metals and minerals appeared too. Around 98% was rock of little value.

Tin processing, also know as ‘tin dressing’ was a complex science. Tin dressing was carried out by breaking the big lumps of tin bearing rock that came out of the mine and separating out the small crystals of tin. This was done in several stages, as the rock was ground smaller and smaller, with the tin crystals being separated out at each stage.

Tin processing was complex and can be divided into 8 stages: Crushing, Sorting, Grinding, Classifying, Separating, Cleaning, Smelting and Assaying.

Time Challenge

 

 Photograph reproduced with the kind permission of the T Grevatt collection held by Cornwall Council

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