Production crews at the Bootu Creek manganese mine have been laid off as the mine is placed into care and maintenance.
Around 45 workers have lost their jobs at the Northern Territory mine, which was staffed by 200 people, mostly FIFO workers.
The redundancies were reported to the ABC by an anonymous worker, who said staff were informed last Friday the mine would be placed into care and maintenance.
It is expected other OM Manganese operations will conclude once stockpiles have been exhausted.
OM Holdings stock prices have dropped from $0.29c in June to the current price of $0.10c.
The company has not announced the closure to the ASX, with the most recent investor presentation given at the International Ferro-alloys Conference in November showing OM Holdings was focussed on the OM Sarawak smelting plant in Malaysia
Earlier in the week the BHP spinoff company South32 announced plans to lay off more than 400 workers from manganese operations in South Africa.
Prices for manganese, a key steel-making ingredient, have continued to slump since the announcement of plans for the South32 demerger in August 2014.
Investors have been left holding the bag by BHP as South32 shares have faltered dramatically since the company launch, trailing from around $2.37 in May down to close at a record low of $1.01 yesterday.