See our: verneuil jewelry.
Auguste Victor Louis Verneuil was a French chemist (1856-1913) He invented a type of blowpipe (chalumeau) with which he was the first to lab produce rubies.
This process is also sometimes referred to as 'flame fusion'. His results were published in 1904. The apparatus is still used today (sometimes in banks of several hundred units) to make synthetic varieties of corundum and other synthetic gemstones.
Other processes were developed but those are used less frequently, e.g. hydrothermal, flux fusion, and Czochralski.