Wallin’s QGold, which holds 51.7% of SMC, has offered shareholders A3.5c per share cash, or $28.8 million for the shares it does not already own.
The offer price represents a 25% premium to SMC’s closing price of 2.8c yesterday.
BRW named Wallin as Australia’s 10th richest person in 2013 with a fortune of $2.8 billion.
The consideration will be funded from Wallin’s cash reserves.
Newly appointed SMC chairman Laif McLoughlin is married to Wallin’s daughter Fiona and is the general manager of his company QCoal.
McLoughlin only joined the board of SMC earlier this month.
In QGold’s bidder’s statement, it said it planned to keep all existing directors of SMC, but delist it from the Australian Securities Exchange.
SMC owns the Woolgar project in Queensland, which has a resource of around 475,000 ounces of gold.
Wallin’s QCoal owns and operates three Queensland coal mines with several others in development.
SMC advised shareholders to take no action until it compiled its bidder’s statement.
Shares in SMC jumped nearly 40% to 3.9c.