Oh!!! This does confuse the issue. I will have to think about which necklace this might refer to.
At first glance, I think this is a reference to the Queen Alexandra 1901 Cartier Indian necklace.
Although the ledger talks about a "diamond resille" and it may refer to the 1904 creation which Franck and LauraM have said had a fringe of rubies and emeralds, the Flameng portrait definitely does not show emeralds and rubies. [If other posters think QA's necklace in the portrait has emeralds and diamonds, then I definitely need a brain transplant]
I suspect that Bury and Menkes have mistaken things - so easy to do when writing a tome or two.