Flame fusion grows synthetic crystals by dropping fine powder through a very hot flame. The melted drops build up a crystal on a pedestal below.
In more detail
Auguste Verneuil announced the process in 1902, so it is also called the Verneuil process. It is still the least expensive and most common way to make synthetic corundum and spinel. Its stones can show gas bubbles and curved growth lines, which natural corundum does not have.
On a grading report
Labs report the stone as laboratory-grown (synthetic). They may not name the method.
Related terms
- Synthetic gemstone: A synthetic gemstone is made in a laboratory and has essentially the same chemistry and properties as the natural gem. A synthetic ruby is ruby, made by people.
- Curved striae: Curved striae are curved growth lines or color bands in a flame-fusion synthetic. Natural corundum grows with straight, angular zoning instead.
- Flux growth: Flux growth is a way to grow synthetic crystals from a chemical solvent (flux). Crystals form as the hot solution slowly cools.
- Czochralski growth: Czochralski growth makes a synthetic crystal from a melt. A seed crystal touches the molten material and is slowly pulled up as the crystal grows.
- Ruby: Ruby is the red variety of the mineral corundum. Chromium causes its red color.