A Rare Rock
One acquisition in 2008 has been a most unusual example of an illustrated notepaper
published by Rock & Co, mysteriously captioned “A Framing Girl, or Racker in Tin Mine”, drawn by Thomas Onwhyn, dated 9th Nov. 1850.
Tin ore, which was mainly an oxide of tin called Cassiterite was mined from lodes about 1 to 2 feet thick sandwiched between granite slabs sloping deep into the ground.
Records show that some 6000 women known as Bal Maidens were employed as surface workers at the Cornish mines during the 1860's to dress this ore prior to smelting. Their jobs entailed rock picking; griddling the ore and feeding the ore to water powered hammers. The resultant black tin slime was then concentrated by washing on the sloping tables illustrated. The young woman would have been responsible for controlling the flow of a 20 lbs batch of tin slime onto the narrow top end of the frame. She would then have raked the slime down the frame while at the same time cutting zigzag channels to allow a controlled flow of water to separate rock waste from the relatively dense Cassiterite.
On completion of this stage the purest tin ore would have remained separated at the top level of the washing frame, and the waste and fines would have carried to the lower end. The Racker would then have tipped the frame around a lengthwise pivot and washed the graded material into boxes beneath the frame. The concentrated Cassiterite in the top box would have contained 70% tin by weight and would then have been considered ready for calcining or smelting. The actual yield of white tin metal, before the introduction of mechanically agitated screens, was a rather meagre 1% of the tonnage hauled from depths of up to 200 fathoms (1200 feet). Nevertheless, some of the mines survived into the twentieth century despite frequent slumps in demand, and competition from overseas.
The above Rock illustration shows the Botallack tin and copper mine circa 1850 complete with winding gear, and pump houses to power the drainage and ventilation.
Q While considering the Cornish tin mining experience I was assailed by a question prompted by the thought that my Racker might be one of a series illustrating a range of tasks such as Ore Picking; Spalling; Griddling, and Wagon Loading. Has anyone seen other examples of Bal Maidens drawn by Thomas Onwhyn?
Keith B Smith