* Workers to resume duties with night shift on Monday
* NUM describes wage agreement as 'biggest victory'
* Plans to cut costs to keep underperforming assets
(Recasts with losses, adds projects)
By Shapi Shacinda
JOHANNESBURG, Oct 18 (Reuters) - A six-week strike over wages at South Africa's Northam Platinum ended on Monday, and the company said the action cost it 380 million rand ($55.31 million) in revenue losses.
It said it planned to resume operations on Tuesday.
More than 8,000 members of the National Union of Mineworkers (NUM) had been on strike since September, after rejecting Northam's 9.5 percent pay rise offer. They were demanding a 15 percent pay rise.
NUM had said the miners who accepted a 10-13 percent improved pay offer, with the exact figure depending on each worker's category, were due to resume operations at Northam's Zondereinde mine later on Monday.
"This is the biggest victory we have achieved at Northam," NUM spokesman Lesiba Seshoka told Reuters.
Seshoka said the union had also agreed to an increase in living allowance to 1,800 rand ($262) from 1,600 rand, while workers in the company's hostels would for the first time receive an allowance of 600 rand per month.
Northam had said the strike was costing it 1,000 ounces per day in lost production of platinum group metals (PGMs).
South Africa, the continent's biggest economy, has been hit by a wave of strikes and strike threats, which have led to pay settlements well above the inflation rate and have raised fears that the cost of living will rise.
South Africa's inflation rate was 3.5 percent in August.
CAPITAL RAISING
Northam said separately in its annual report seen by Reuters that a planned capital raising for its Booysendal project for which it plans issuing a convertible bond would be accelerated from June 2011. The project will cost 3.6 billion rand.
The Booysendal project will add 162,000 ounces of PGMs to Northam, which raised its output in the 2010 financial year by 6.3 percent to 321,475 ounces.
Northam's chairman P. Lazarus Zim said the company was in the process of converting part of its mining rights as required by South African mining laws.
Mining companies were required to convert their mining rights by a set date or lose them altogether after a new mining act took effect in 2004. The new legislation sought to avoid discrimination in the system and to better distribute assets among historically disadvantaged groups.
Northam said its operating margins, which declined to 20 percent from the previous 25.7 percent in the last financial year could fall further in 2011 financial year if costs continued to escalate.
Zim said Northam would not close any underperforming assets, but try to keep unit costs lower and continue to achieve high grades and to extract good recoveries. The company will also continue to uphold higher safety standards.
South Africa, the world's biggest producer of platinum and ferrochrome and the fourth-largest gold miner, has a dire mining safety record compared with the industrialised world, partly because it has some of the deepest mines.
Last year, 165 miners died in South African mines.
Northam said capex at the key Zondereinde mine is expected to be around 340 million rand mainly for a mine deepening project. (Editing by Jane Baird and James Jukwey)