Green Quartz is also known as Praseolite and by the trade name of Greened Amethyst. Part of the Quartz family, Green Quartz is the result of Amethyst that is heat-treated until the color turns transparent green. Naturally occurring Green Quartz is very rare and color can range from a yellowish green to mint green. Clean with warm, soapy water. Avoid use of steam cleaner. Use of ultrasonic is usually safe.