One of the more famous cases of a gemological slip-up, the Imperial State Crown of England features many beautiful and rare stones, including the 317 carat Cullinan II, Saint Edward’s Sapphire, and the Black Prince Ruby, which dates to the 14th century. However, it wasn’t discovered until modern times that the 170 ct Ruby (about the size of a chicken egg), is actually a very fine Spinel! The stone by convention is still referred to as a ruby.
for more info, check out our precious gemstones pages!