Curved striae are curved growth lines or color bands in a flame-fusion synthetic. Natural corundum grows with straight, angular zoning instead.
In more detail
With round or elongated gas bubbles, curved striae point to a flame-fusion stone. They can be hard to see in pale stones. Immersion or short-wave ultraviolet light helps a gemologist see them.
Related terms
- Flame fusion: 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.
- 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.
- Color zoning: Color zoning is uneven color in a gem: bands or patches of deeper and paler color.
- Inclusion: An inclusion is a clarity characteristic inside a diamond, or one that reaches the surface from inside.