Sunshine Silver Mining and Refining is designing a mill with roughly twice the capacity assumed in its initial mine plan, seeking room to expand production after a targeted late 2028 restart of the Sunshine silver mine near Kellogg in Idaho’s Silver Valley. The proposed plant would process up to 2,000 tonnes a day against about 1,000 tonnes in the initial assessment, according to the company’s second quarter filing. Crews are dismantling the old mill, a new hoist has been installed and underground equipment purchased.
The initial assessment estimated capital spending at $286.9 million for the smaller operation and forecast average annual silver production of 6.7 million ounces over the first five years of a 24 year mine life. Those numbers do not describe the larger plant. Sunshine raised $310.5 million gross in its June initial public offering, with net proceeds of $286.5 million, and says the site carries about $600 million of existing infrastructure, of which roughly $290 million of spending is needed to return to production. A mine and mill feasibility study due in the second quarter of next year, followed by a final investment decision, must establish whether the deposit supports the higher throughput and what the larger restart costs.
The resource case for a bigger mill rests on conversion. The February estimate outlined 3.16 million indicated tonnes grading 1,022 grams of silver per tonne for 103.9 million ounces, and 6.41 million inferred tonnes grading 776 grams for 159.8 million ounces. A 50,000 metre underground drilling programme, due to finish this month, aims to upgrade inferred material into the indicated category for the feasibility study. The company expanded its mineral rights holdings by 60 percent to about 154 square kilometres in September and plans a separate 45,000 metre surface programme across East Sunshine, Pine Creek and Rock Creek.
Two refining studies due in the first half of next year add a second leg: a new antimony plant that could produce up to 35 million pounds, about 15,900 tonnes, of finished antimony a year, and a restart of the existing silver copper refinery, which has nameplate capacity of 10 million ounces of silver a year. Major permits for the antimony plant are in place. Both projects remain subject to feasibility work and investment decisions.