Diversified miner South32 has reported a solid production performance in the December quarter, with the miner maintaining its production guidance for the full year to June 2019. “We achieved a strong quarter of production, maintaining full-year guidance for all operations with the exception of Illawara metallurgical coal, where improved longwall performance has underpinned a 7% increase to our prior estimate,” South32 CEO Graham Kerr reported on Thursday.