Precious metals mining company Sibanye- Stillwater on Tuesday announced the impending launch of a $450-million convertible bond offering linked to the refinancing of the outstanding portion of the bridge loan the company raised to buy Stillwater Mining in the US. The senior unsecured guaranteed convertible bonds, which fall due in 2023, will be issued by the company on September 26, underpinned by the Stillwater and Kroondal operations.