EXHIBIT 99.1

JOINT FILING AGREEMENT

Each of the undersigned hereby agrees that this Amendment No. 16 to the statement on Schedule 13D is being filed with the United States Securities and Exchange Commission on behalf of each of the undersigned pursuant to Rule 13d-1(k) under the United States Securities Exchange Act of 1934, as amended.

Dated: August 5, 2015

Glencore AG
	By:	/s/ Martin Haering
	Name:	Martin Haering
	Title:	Officer
	By:	/s/ Stefan Peter
	Name:	Stefan Peter
	Title:	Officer

Glencore International AG
	By:	/s/ Martin Haering
	Name:	Martin Haering
	Title:	Officer
	By:	/s/ Stefan Peter
	Name:	Stefan Peter
	Title:	Officer

Glencore plc
	By:	/s/ John Burton
	Name:	John Burton
	Title:	Company Secretary