The output of limestone – a key raw material for the steel industry - was also lower at 9.6 million MT (worth RO 15.091 million), down from 14 million MT in 2018 (valued at RO 15.7 million). ... ended in 2017 following the closure of the smelter of Oman Mining Company (OMCO) near Al Jizzi. Around 264 tons of copper cathode were sold by …