I have checked the dates in 1910-11 when Queen Mary received the Cullinan diamonds and the Cambridge emeralds. It all happened in a 6 month period. At the same time Garrards was approached to make both her crown for the coronation as well as a tiara she could take to India. [George V had to have a new crown made to take to India as he was not able to take his crown out of the United Kingdom]
The Cullinan diamond was found in South Africa in 1905 & given to Edward VII in 1907. It was cut in Amsterdam in 1908 & the smaller stones were kept by Asschers in Amsterdam.
06/05/1910 Edward VII died May-Dec 1910 All Cullinan cuttings bought by S African Govt from Asscher & given to Q Mary as a gift to commemorate the Union of S Africa
Oct 1910 Francis of Teck dies & Q Mary pays his mistress to get back the approx. 30 emeralds that had belonged to their grandmother