Spinel is most famous for its deep red variety that closely resembles ruby and the two gemstones can be very difficult to distinguish. Until the late 19th century, there was no distinction made between Ruby and red Spinel, as they look identical and are found in the same localities, commonly Sri Lanka and Burma . Many famous old "Rubies" were discovered to be in fact Spinel. For example, the enormous "Ruby" that forms the centrepiece of the royal crown of England (the Black Prince's Ruby) was actually determined to be Spinel.