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Stolen diamonds can all too easily be sold on to unsuspecting buyers. So to
help establish the real owner, Gersan of Liechtenstein has found a way to
engrave their name onto jewels without without spoiling their appearance (GB
2361671). First, the gem is coated with a fine layer of gold. It is then mounted
in a vacuum chamber where the gold layer acts as an electrode that attracts a
high-energy beam of charged ions. The beam can be steered to write the person’s
name. Molten potassium nitrate is then used to remove the gold coating, leaving
the diamond surface smooth except for the owner’s name in a 30-nanometre-deep
groove. The mark is invisible to the naked eye but shows up under a
microscope.