The steady and sharp fall in coal prices has knocked down shares of big mining companies like BHP Billiton (NYSE: BBL - news ) , Glencore (Xetra: A1JAGV - news ) and Rio Tinto (LSE: RIO.L - news ) , and it has seen many financers exit the sector.
Take context from the input text and decide on the accurate relationship between 'Glencore' and 'mining' from the options provided.
Options: industry, chairperson, stock exchange, product/material produced