Ametrine, also known as Trystine, is a quartz-based combination of amethyst and citrine, which appears in yellow, orange and purple and has a Mohs scale of hardness of 7.
Ametrine is a tough stone, making it ideal for the jewelry industry, and while it varies in size, its color zoning is best evident in gems weighing seven carats and over.
Ametrines can be lab-grown, but such gems have accurate color zoning, compared with the “bleeding” which occurs in natural ametrines. Industrial ametrines are usually cheaper than natural ones, but they come in a wider range of colors and include shades of green and blue.
Ametrines are mined mainly in Bolivia, but commercial-grade deposits have also been found in Brazil and India.