The dispute over the "Idol's Eye" diamond pitted art collector Sheikh Hamad bin Abdullah Al Thani, cousin of Qatar's ruler Sheikh Tamim bin Hamad Al Thani, against the relatives of former culture minister Sheikh Saud bin Mohammed Al Thani.
QIPCO's lawyers say that a 2020 letter sent by the Al Thani Foundation's lawyer amounted to an agreement to sell the diamond for $10 million, but Elanus said the letter was sent by mistake.
Sheikh Saud, Qatar's minister of culture between 1997 and 2005, was one of the world's most prolific art collectors and bought the 70-carat Idol's Eye diamond in the early 2000s.
The two sides had disagreed over how much the gem is worth, with Elanus' lawyers saying in court filings that an expert had valued the diamond at around $27 million (£21 million).
The agreement gave QIPCO the option to buy the diamond with the consent of Elanus Holdings, a company linked to Sheikh Saud's relatives.
