Amethyst is a gem that is formed by introduction of iron in quartz crystalsa mineral composed of silica (SiOtwo or silicon oxide). The general formula of amethyst is SiOtwo::Faith3+presents a violet color and its name comes from the Greek ἀμέθυστος (amethystos"not intoxicated"), a name derived from its use as an amulet against various types of intoxication in ancient Greece, especially alcohol intoxication.
Amethyst is considered a semiprecious stone and it is one of the most used and appreciated varieties of quartz in jewelry. The color can vary from light violet to dark violet and have secondary red, blue and green hues.
The color is given mainly by the presence of iron III atoms (Fe3+) that substitute silica atoms in the crystal structure of quartz (crystalline system trigonal trapezohedral). The different shades are due to the greater or lesser amount of iron and the presence of transition metals, generally in trace amounts.
The amethyst has volcanic origin. It is formed in magmas of siliceous rocks that are mixed with iron oxides from other minerals. The temperature at which typical amethyst forms does not usually exceed 300 – 400ºC; above this temperature the amethyst loses its violet color and turns yellow, orange above 500 ºC (known as burnt amethyst).
Amethyst is usually found inside geodes (rock cavities) along with other types of quartz. Some of the highest quality amethyst deposits are found in Siberia, Sri Lanka and Brazil.
synthetic amethyst
There is synthetic amethyst formed in laboratories under controlled conditions. The process followed for manufacturing is known as growth or hydrothermal synthesis. It is carried out under high pressure inside autoclaves where rock crystal (a very pure variety of quartz) is placed together with iron impurities and subjected to radiation with gamma rays, X-rays or electron bombardment.
The synthetic amethyst tries to imitate the highest quality amethyst (75-80% violet, rest blue and secondary red tones), it has the same physical and chemical characteristics and it is very difficult to differentiate it from natural amethyst, practically impossible without sophisticated gemological tests generally of cost. very high.
Synthetic quartz crystals are widely used in watches and other electronic devices, while synthetic amethyst is used almost exclusively in the world of jewelry.