Okorusu fluorspar mine in Namibia will close in November making 407 people redundant.
The mine, which is located in Otjiwarongo in the Otjozondjupa region, produces fluorite specimens that are sold on the international market. Solvay bought the operation from Okorusu Fluorspar in 1988.
The company previously produced 132,000t of 97% pure acid-grade fluorspar concentrate a year, which later stabilised at 120,000t; however, the demand dropped due to the global economic crisis in 2009, reported The Namibian.
Okorusu fluorspar mine's managing director Mark Dawe said: "After 26 successful years, the viable higher grade ore resources are now depleted, resulting in production that is no longer economical."
The mine is to be put under maintenance and care during which time it will go through a period of intensified exploration and metallurgical research and development to explore the feasibility of low-grade ores and new resources, the company said in a statement.
"The possibility of restarting mining and processing operations will depend on both the successful outcome of this intensified research and development work as well as on improved market conditions and pricing for acid-grade fluorspar," Dawe added.
There are 321 full-time employees and 86 contractors currently working at the mine. Solvay has said that all staff will be given an appropriate notice of the termination of their employment.
Minister of Mines and Energy Isak Katali told The Namibian: "[The company] have been researching to find the right metallurgy to recover it, but so far no solution has been found.
"While they continue to do research, they will also explore the new exploration prospecting license (EPL) to find more ore body and re-open the mine."