Dragonflies made of electroplated Kyanite in gold color in a beautiful black box.

The mineral kyanite or disthene is an aluminum silicate with the chemical formula Al2SiO5. It belongs to the group of nesosilicates. The blue, gray, white, green or black mineral has perfect cleavage along the crystal plane [100], a white stripe color and a glass to pearl luster. The crystal system is triclinic, the average density is 3.61 and the hardness is 4 to 7. Kyanite is neither magnetic nor radioactive. The name of the mineral kyanite is derived from the Greek word kyanos, meaning "blue". Kyanite is a very common mineral as part of many rocks. It occurs, among other things, in metamorphosed sedimentary rocks. It is also, together with the other aluminum silicates sillimanite and andalusite, an indicative mineral for the depth and temperature at which a rock has undergone metamorphosis. Kyanite is usually stable at temperatures below 650 °Celsius and at pressures above 0.3 GPa (gigaPascal). The pressure and temperature are related, so at high pressure (0.6 GPa) a higher temperature (600 °C) is required to form sillimanite from kyanite. At pressures below 0.3 GPa, andalusite is the stable aluminum silicate. Gem quality kyanites occur in India, in the gemstone deposits of Myanmar and Korea. In the United States, kyanites are mined in California, Tennessee, Georgia, New Hampshire and North Carolina. In Africa, kyanite occurs in Kenya, Tanzania, in Europe in Russia, Switzerland, Austria and France. Kyanite occurs in the sand fraction of Dutch Quaternary river sediments. In the heavy mineral analysis that took place in the Netherlands at the National Geological Survey during the second half of the twentieth century, the mineral is classified in the so-called stable group. Only the name disthene is used in this study.