What is the relationship between Petra Diamonds and diamond in the context of the input sentence. Choose an answer from: 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.

Let’s speed up spread of broadband by separating Openreach from BT Crown jewels miner Petra Diamonds loses its sparkle The precious gem producer has seen a sharp fall in sales and profits as weak Chinese demand has sent diamond prices lower Petra Diamonds unearthed the gem which now adorns the Sovereign's Sceptre, part of the British crown jewels collection.

Answer: industry