In which decade were the first flame-fusion star rubies produced?

The production of flame-fusion star rubies began in the 1940s, marking a significant advancement in gemstone synthesis. This method involves melting aluminum oxide with the addition of other materials to create synthetic corundum, which can then be treated or cut to exhibit the characteristic star effect through the presence of inclusions, such as rutile needles, within the stone.

The 1940s saw the advent of techniques that allowed for more consistent production of such stones, making them more accessible and altering the landscape of the colored gemstone market. Prior to this decade, the technology and knowledge necessary for producing synthetic stones were not yet sufficiently developed, placing the inception of flame-fusion star rubies firmly within this timeframe.