The Koh-i-Noor diamond

A 105.6-carat diamond in the British Crown Jewels, said to bring bad luck to men who wear it, whose ownership is disputed.

Historic Royal Palaces says the Koh-i-Noor weighs 105.6 carats and is set in the Queen Mother's crown of 1937. It has also said the stone is thought unlucky for men to wear because of its bloody past.

Wikipedia says the curse rumour may have started in the Delhi Gazette and was soon picked up by The Illustrated London News, and that Queen Victoria herself voiced concern about it. That produced a second rumour, that the curse fell only on male rulers.

Ownership of the stone is disputed. The Guardian reported in 2000 that the Taliban asked the Queen to return the diamond to Afghanistan for display in Kabul's museum. BBC News reported in 2016 that the Indian government said it still wanted the stone back, after earlier telling India's Supreme Court something different. In 2023 the BBC reported that the diamond would not be used at the coronation, noting the disputed ownership and worry about a diplomatic dispute with India.