On Tuesday, the thieves broke into the gold storage units at the mine, which is located in northwest South Africa, according to published reports.
“The gold was stored at the mine under heavy security," spokeswoman Lauren Forie told Bloomberg News. “It was a brazen attack, luckily nobody was hurt.”
The stolen gold is valued at roughly US$518,000 at recent pricing levels.
Shares in Harmony Gold shed 6.9% in morning trade to US$2.15.