The black economic empowerment (BEE) group is paying ZAR 1.6bn ($151m) for the stake.
The investment, along with an earlier issue of 96m new shares that raised ZAR 2.4bn, will be used to fund capital infrastructure projects.
The Brimstone led investment was welcomed by Grindrod chief executive, Alan Olivier, who said he was “looking forward to their valuable input.”
Brimstone has a 59% share in the BEE consortium, Calulo Investments Pty 20%, Solethu Investments Pty 13%, Safika Holdings Pty 5% and Adopt-A-School Foundation 3%.
Calulo, Adopt-A-School and Solethu were existing shareholder in Grindrod subsidiaries and have restructured their stakes to the listed company level.
Both Grindrod and Brimstone are Johannesburg stock exchange listed companies.
Brimstone’s chief executive, Mustaq Brey, said Grindrod was a long term investment in African infrastructure development which he described as “an attractive and growing asset class."
“Grindrod shares are currently tightly held and it’s difficult to acquire a substantial shareholding in the company. The BEE Transaction enables us to acquire a meaningful stake on a leveraged basis and we look forward to contributing to the company’s ongoing success,” added Brey.
Grindrod through its Island View Shipping and Unicorn Shipping subsidiaries owns a diverse fleet of 23 ships with chartered in tonnage lifting the total fleet to 35 vessels.
Black controlled and managed Brimstone has previously focussed on businesses in the food, healthcare and financial services sectors.
But Brey said the Grindrod investment established infrastructure as a new focus area.
Johannesburg based Brimstone employs 3,300 directly and 16,000 in associate companies.
Financial sector investments include Lion of Africa Insurance, Old Mutual, Aon Reinsure, Nedbank and Smart ATM.
There are also stakes in hospital operator Life Healthcare, technology company Hot Platinum as well as clothing companies House of Monatic and Queenspark.
