"Apple removed 18 smelters and refiners in 2019 for flouting conflict mineral code of conduct", 6 February 2020.

Apple in a report on mineral sourcing...said 18 smelters and refiners that were not willing to participate in third-party audits were removed from its supply chain in 2019, resulting in a 100% audit participation rate for the fifth consecutive year. In a disclosure to the U.S. Securities and Exchange Commission, Apple detailed efforts to responsibly source so-called conflict minerals — tin, tantalum, tungsten, gold (3TG, collectively) and other minerals...

As defined by law, conflict minerals include 3TG and other common minerals used to finance conflict in areas like the Democratic Republic of Congo...At the end of 2019, Apple found none of its recognized 267 smelters and refiners to have sourced 3TG that directly or indirectly funded armed groups in the DRC or adjoining countries. Of those 267 entities, 24 were known to be sourcing from the DRC or a nearby country...Apple requested the removal of 18 smelters and refiners for failing to meet predefined standards including participation in third-party audits, acting on corrective action plans or meeting Apple's supplier code and requirements...Members of Apple's supply chain must follow the company's Supplier Code of Conduct and Supplier Responsibility Standard on the Responsible Sourcing of Materials, which requires suppliers to "engage with smelters and refiners to assess and identify a broad range of risks beyond conflict, including social, environmental, and human rights risks."...