|Sands are treated in the Sand House
The sands from the screens are treated on SHAKING TABLES. The narrow ridges,or 'riffles', are so designed that the light 'tailings' flow over them and off at the bottom of the table, while the concentrated tin is thrown along the top; 'middlings', consisting partly of tin and partly of other impurities, go on for further crushing . Each table has its own particular characteristics: its tilt, the speed of vibration and flow of water a1l contributing to the quality of the tin produced. So you will notice that the concentrated tin will appear differently on each table.
'Middlings' are ground even finer by BARREL PULVERISORS. These contain a large quantity of steel balls, or quartz and flint pebbles, or even scrap iron, all of different sizes, which churn round with the drum, crushing the 'middlings' beneath. The finer the sands are ground the more tin is released, but, paradoxically, the more is lost with the waste.
The sands and slimes from the Pulverisor again need to be separated. A RAKE CLASSIFIER does this by dragging up the coarse sands with the rake, allowing the slimes to overflow and pass down to the Settling Pits. The sands go on to more Shaking Tables for further grading and recycling. From them the concentrate is extracted as before and the middlings return to the Pulverisor for further crushing.
Slimes are treated in the Slime Plant
First of all the fine tin slimes are allowed to settle in SETTLING PITS, where the water is drained off and they become thickened.Then the exact amount of water required can be added at a controlled rate. The action of sun, air, wind and the light spray of water on the settling slimes is not fully understood, but they all help to break up the tin particles.
|History of Tolgus||Stream Tin & Lode Tin||Management & Workers||12-headed Cornish Stamp||Sulpher & Arsenic Waste Disposal.|
|Water Power||The Sand House||The Slime Plant. Assaying.||Smelting||Trevithick Trust|
|TOLGUS Tin streaming at Redruth|