Apple Inc. has reached what it’s calling a milestone in supply-chain transparency, saying it’s now auditing 100 percent of its suppliers for the use of conflict minerals linked to violent militia groups in the Democratic Republic of the Congo... [While] it isn’t yet declaring its products totally conflict-free, the company said all of its 242 smelters and refiners of tin, tantalum, tungsten and gold are now subject to third-party audits...

“We could have very easily chosen a path of re-routing our supply and declared ourselves conflict-free long ago, but that would have done nothing to help the people on the ground,” Apple Chief Operating Officer Jeff Williams said. “We chose to engage with as many smelters as possible..." 

To reach a fully audited supply chain, Apple spent five years “cajoling, persuading, and even embarrassing suppliers by publishing their names,” Williams said... Though all of its smelters and refiners are now audited, Apple says it stopped short of declaring itself conflict-free because it wants to focus on improving issue resolution and responses to incident reports...

[also refers to steps taken by Intel, Kemet]