Achroite is a member of the elbaite group of tourmalines. Elbaite is a sodium, lithium, and aluminium borosilicate, which was originally discovered on the Island of Elba, Italy in 1913. Achroite is extremely rare; the most rare variety of tourmaline, however there is not much demand for the stone as it is rarely used in jewelry. In fact, achroite is the least expensive variety of tourmaline. Collectors however, prize the stone, as it is very unusual for a tourmaline to display no color as achroite does. The name achroite actually comes from the Greek words achroos, meaning without color.
Achroite is a fibrous variety of tourmaline, which can either occur naturally, or can be produced by heating pale pink tourmaline. Occasionally, achroite can be found with a small spot of color within the clear material. These stones are more valuable and can be very beautiful if cut the right way. Because achroite is clear, and does not display the strong dichroism that most varieties of tourmaline display, it can be cut in any direction. Achroite is said to be a stone that represents modesty. It helps the wearer gain a clear perception and understanding of life. It has also been said that the clarity of the stone facilitates communication with the angelic realm.
Achroite is a high pressure, high temperature mineral, like other tourmalines. Achroite is a brittle stone, and rates a 7 to 7.5 on the hardness scale. It has a vitreous luster, and is opaque to transparent. It is usually cut into brilliant or mixed cuts. Achroite is different than its other tourmaline relatives, as it is piezoelectric. Piezoelectricity means that when the crystal is heated, an electrical charge or vibration is created at opposite ends of the crystal.
Achroite is commonly found in granite pegmatites or in granites that have undergone metasomatism by boron-bearing fluids. The stone can also be found in sediments near these granites, and as an accessory mineral in schists and gneisses. Achroite can be found in pegmatites in Madagascar and in California, with other colored tourmalines. The major source of achroite is in the mines in Saint Austell, Cornwall, in southwest England. However, it can also be found in Androscoggin County and Oxford County, in Maine, as well as in various locations around the United Kingdom and Afghanistan.
