The Cullinan 1 is part of a larger diamond that was gifted to the Royal Family after it was mined in 1905.
Otherwise known as the Great Star of Africa, it was discovered while South Africa was under British rule.
But after Queen Elizabeth II's death, there have been growing calls for the diamond to be returned to the place it was discovered.
South Africa's President Cyril Ramaphosa offered his condolences – but more than 6,000 people have signed a petition calling for the diamond to be returned and put in a museum.
Queen Elizabeth II's sceptre resting on the top of her coffin
POOL
Queen Elizabeth II holding her sceptre
Wiki Commons
Currently held on the end of the late monarch's sceptre, there has been plenty of debate about who actually owns the diamond.
Former ANC KwaZulu-Natal provincial secretary Thanduxolo Sabelo said: “The minerals of our country and other countries continue to benefit Britain at the expense of our people.
"We remain in deep, shameful poverty, we remain with mass unemployment and rising levels of crime due to the oppression and devastation caused by her and her forefathers.
"The Cullinan Diamond must be returned to SA with immediate effect."
And African Transformation Movement (ATM) MP Vuyo Zungula, went further still.
He told timeslive.co.za: "SA should now leave the Commonwealth, demand reparations for all the harm done by Britain, draft a new constitution based on the will of the people of SA not the British Magna Carta, and demand the return of all the gold, diamonds stolen by Britain."
It comes as Queen Elizabeth II is Lying-In-State – and will be for 24 hours a day until closing at 6.30am on Monday, ahead of the state funeral in Westminster Abbey.
There will be a national bank holiday to allow as many people as possible to see.
Queen Elizabeth II’s final resting place will be the King George VI memorial chapel, an annex to the main chapel – where her mother and father were buried, along with the ashes of her sister, Princess Margaret.
Prince Philip's coffin will move from the Royal Vault to the memorial chapel to join the Queen’s.