Cutting Ametrine Gemstones
The artists who cut ametrine plan their cutting to produce gemstones that display both the purple amethyst and golden citrine. The most popular cut is a rectangular gemstone that is close to 50% amethyst and 50% citrine. There is often a slight color gradient area between the amethyst and citrine. Because of this tiny stones of only a few millimeters are rarely cut. They are not large enough to show both purple and golden color. It takes a stone of at least several millimeters in size to show a strong amethyst purple on one side and a strong golden citrine on the other. Rough with a sharp transition between purple and golden is the most desirable.
What Gives Ametrine Its Color?
The colors of natural ametrine are produced by iron impurities within the quartz. The purple and golden colors are a result of different oxidation states of iron impurities. Some purple/golden ametrine is produced in a laboratory by heat treating natural amethyst to alter the oxidation state of the iron in parts of the rough. Sometimes a color change is induced by irradiation or irradiation followed by heating.
Some synthetic ametrine is produced in a laboratory by growning "quartz" crystals with zones of various colors. Sometimes a purple/golden material is produced but synthetic stones in a variety of color combinations are grown. These bicolor "quartz" stones are almost always synthetic.
Uses of Ametrine
As a variety of quartz, ametrine is very hard, at seven on the Mohs Hardness Scale. This hardness along with a lack of cleavage makes ametrine suitable for almost any jewelry purpose, including rings and bracelets that might encounter accidental impact. Many consider ametrine to be an elegant but inexpensive gemstone.