Sugilite is a rare mineral of fairly recent discovery. It is named after the Japanese geologist, Ken-ichi Sugi, who first identified it in 1944. It has a distinctive purple color and is usually opaque to translucent. Sugilite has sometimes been called purple turquoise although there is no really no connection at all between sugilite and turquoise.
Although sugilite was first discovered in 1944, it did not become of interest to the gemstone world until many years later. In 1979 a major deposit of gem-quality sugilite was found in a manganese mine in the Southern Khalahari Desert. This important deposit yielded several thousand kilograms of material.
In mineralogical terms, sugilite is classified as a cyclosilicate, in the same class as tourmaline, iolite and the beryl group. Sugilite has a very complex chemical composition, it is potassium sodium lithium iron manganese aluminum silicate. It is only rarely found as crystals, usually being massive in form. Sugilite has a Mohs hardness of 5.5 to 6.5 and a specific gravity of 2.75 to 2.80. It has a refractive index of 1.607 to 1.61 and typically has a waxy to vitreous luster. Sugilite is not especially hard, but is quite a durable material since it has poor cleavage.
Sugilite gemstone colors include all shades of purple; from lilac to plum, including hues of magenta, purple and red-violet. Sugilite specimens often contain black matrix, and reddish or yellowish blotches, since it occurs in brownish-yellow and pale pink as well as violet and reddish-violet. Sugilite cabochons are often be found mixed with chalcedony.
Sugilite deposits are found in Australia, India, Japan, Canada and South Africa.
Like most colored stones, sugilite's value is based on its color. Specimens with a vivid and intense purple are valued most highly. Since many sugilite specimens are multicolored, attractive patterns and veining raise the value of a piece. Sugilite is often available in large sizes, with pieces weighing over 10 carats being common.