16 December 1954 CE
A press makes the hardest natural material.
Read the full sourced page: The First Lab-Grown Diamond
Myth: undefined
Reality: They are diamond: carbon in the same crystal structure as a mined stone. Gem labs such as IGI and GIA grade them and note that they are laboratory-grown.
Myth: undefined
Reality: ASEA in Stockholm made diamond on 16 February 1953 but did not report it. General Electric's 1954 synthesis was the first commercially successful one and the first announced.
The Gem Tray is another reference site by the same author.