Back to Materials Amethyst Amethyst is a type of quartz (silicon dioxide). The purple colour comes from iron and aluminium impurities which interact with each other. Amethyst in nature is produced by heat and pressure near to volcano`s and is a natural crystal. This type of mineral has been used in jewellery making since before the roman times. Amethyst used to be one of the precious gemstones, but due to larger finds in mining, and the ability to synthesize amethyst with special equipment, it as now classed as a semi-precious gemstone. The quality of amethyst can still lead to either hugely expensive stones with purfect clarity, or to a bead that is good value and easy to purchase from many suppliers. Amethyst has a specific gravity of approximately 2.65 (2.65 times the weight of water by volume) which is quite an average value for minerals, and its hardness value is 7.0 on the mohs scale. Amethyst can be heat treated to create a fake citrine although the fake citrine has a red tinge rather than being a natural yellow shade, due to the iron content. Amethyst is the birthstone of February, and is associated with the 17th wedding anniversary.