From Fox Business.

A thousand mine workers at three Glencore Xstrata chrome mines in South Africa were fired last week for illegally going on strike, bringing mining operations to a standstill northeast of Johannesburg in Limpopo province, the company said Monday.

The dispute at the mines near Steelpoort adds to long-running friction in the mining industry that caused a slowdown in production, raised concerns about Africa’s largest economy and sent the rand to fresh four-year lows, according to a Fox Business report.

Chromium is a raw material used to produce ferrochrome, a key ingredient to make stainless steel.

The strike started last Tuesday but supplies to customers have not yet been affected, said Christopher Tsatsawane, a spokesman for the company’s chrome operations.

Most of the miners belong to the militant Association of Mineworkers and Construction Union and they stopped working in solidarity with a person who says he was assaulted by a shift supervisor, the company said last week.

Tensions between AMCU and the dominant National Union of Mineworkers are expected to increase as they battle for members.

Employers often hire back most of the workers they fire, according to the Fox Business report.

South Africa has about three quarters of the world’s chromite reserves.

Read more at Fox Business.