Utilize the input text as a context reference, choose the right relationship between Glencore and mining from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

"However, funds that track the FTSE 100 have had to invest in Glencore and mining stocks because they make up such a large part of the index.

Answer: industry