The pristine weapons were stumbled upon by a team of researchers while they were photographing an ancient inscription on a stalactite.
Petra Diamonds has found yet another notable gem in the Cullinan mine, just two weeks after its rare blue diamond was sold for around R580 million.
A 1,098-carat diamond, which Botswana claims is the third-largest gem-quality stone ever found, was unearthed on June 1.