JOHANNESBURG — A mining company says it has found a rare blue diamond in South Africa.

Petra Diamonds says the 29.6-carat diamond came from the Cullinan mine, source of some of the world’s most famous diamonds. Cullinan lies near Pretoria, the South African capital.

Petra Diamonds said in a statement Tuesday that the diamond is a vivid blue with extraordinary tone and clarity, and could yield a polished stone of great value.

The Cullinan mine yielded the 530-carat Star of Africa blue diamond that is part of the British crown jewels.