diamond necklace associated with harzburgites is about 3.3 billion years old -- more than two thirds the age of Earth itself.
First the diamond jewelry are weighed in a vacuum. Next the colour is determined. The clarity is then estimated only after the diamond fashion have been magnified by 10 times.
Most Tiffany Style Diamond were formed more than 100 miles below the surface of the Earth, some from perhaps 400 miles down.