Utilize the input text as a context reference, choose the right relationship between 'Escondida mine' and 'Copper' from the options.
Options: manufacturer, product/material produced, distributed by, chairperson

Copper is selling for around $2.47 a pound, not far off a six-year low, while BHP's output will also fall next year due to lower grades at its Escondida mine in Chile.
product/material produced