Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
In 2017, the term sapphire jubilee or blue sapphire jubilee was coined for the celebrations to mark the 65th anniversary of the reign of Queen Elizabeth II (see Sapphire Jubilee of Elizabeth II). Previously, the sapphire wedding anniversary was understood to be the 45th, and this would be expected to carry over to regnal anniversaries as with silver, golden, and diamond jubilees.