The union also said on Tuesday that further one-day protests will be held in other provinces in the coming months, although the extent of those will depend on the severity of local safety concerns.
The protests will lead up to a national one-day protest in September or October.
North-West Province is home to many of the country's platinum mines and some gold operations.
"The National Executive Committee has noted with great concern the increased rise of mine fatalities in the mining industry, especially gold and platinum," Frans Baleni, the NUM's general secretary, told reporters.
He said mine fatalities have risen 27 percent in the first quarter of this year compared with last year, in line with government figures.
While some operations may be affected by the Saturday protest, he said the impact during the nation-wide event would be bigger: "It will be a total shutdown."
He also said the union, South Africa's main mining union, would call on other smaller labour groups to participate in the national action later this year.
Baleni said the union would only call off the national protest if companies committeed to a zero-fatality record.
South Africa, which has the world's deepest gold mines, has a dire safety record compared to the industrialised world and deaths have led to temporary closure of mines, denting output.
Some South African gold mines are nearing depths of 4,000 metres, making access and drilling dangerous in harsh conditions in which rock temperatures can reach about 50 degrees Celsius.
Still, the number of miners killed in South Africa has fallen drastically over the last two decades.
New legislation in the last 16 years has increased miners' rights and more than halved fatalities to 128 in 2010, but reducing deaths has been gradual given the labour-intensive nature of the sector and its poorly educated workforce.
Companies have invested heavily to improve safety, even shutting mines for months at a time, in a bid to dismiss claims by unions that they were putting ounces before lives. But analysts have said it is unlikely they will reach a zero-harm record in the near term.