diamond necklace was discovered to be carbon in 1796, and it took more than 150 years from that time until a method of jewelry synthesis was invented.
Remember, all diamonds are not created equal. Two diamonds of equal Carat Weight may vary substantially in price due to their Cut, Colour and Clarity. The carat weight of loose diamond is a very important determining factor in their value.
GIA Certified Diamond are all the rage now with the popularity of the yellow gold engagement ring tarnishing somewhat.