Everest Mining's assets will be transferred to Northam for a cash consideration of R400m ($32.9m), under a Part A sale.
The process is likely to be implemented on 26 June this year.
Northam CEO Paul Dunne said: "The Part A completion gives Northam management early access to the Everest assets, and gives us the opportunity to start the integration process with the existing Booysendal operation.
"With the conclusion of this step, we will be in a position to start extracting value and developing the new Booysendal South mine."
According to Part B of the sale announcement made in February, Everest Mining rights will be later transferred to Northam for ZAR50m ($4.1m).
Part B of the sale must receive approval from the Minister of Mineral Resources.
Everest Mining's assets are ideal for Northam's Booysendal Division, in terms of location and operations.
Unfavourable market conditions had compelled the South African subsidiary of Aquarius Platinum to place its assets on care and maintenance in June 2012, before announcing the sale.
The company's mining assets include one concentrator facility with a nameplate throughput capacity of 250,000t a month. It also comprises a chrome spiral recovery plant, a tailings dam and three decline shaft systems situated on the Everest Mining area.