Strictly speaking this is a jewels of the day post. Kate got to trot out not only a tiara, but bracelets loaned by the Queen from her personal (very personal) collection.
Kate wore the Lotus Flower tiara, previously beloved by the Queen Mother and Princess Margaret, and fitting theme to welcome the Chinese. But perhaps more attention was on her two diamond bracelets. Her left wrist was adorned by Prince Philip’s wedding gift to Elizabeth (also designed by him from jewels owned by his mother), The piece on her right wrist was a 1932 piece made by Garrard and refashioned from a choker worn by Queen Mary to a bracelet redesigned to Queen Elizabeth, the Queen Mother’s specifications. No word on where the earrings came from, but they added to the overall blinginess of the occasion.

Kate wore the earrings in Los Angeles back in 2011. It is said they are on loan from QEII.
Thanks for this info! They are really not handing over very much but I can understand why.