Kyanite: the Multi-hardness Mineral

     Kyanite, which is also called “cyanite,” “rhaeticite” and “disthene” is a polymorph of a chemical called aluminum silicate. In my post about polymorphs I mentioned that I had a few polymorphous minerals to blog about and now I’ve finally gotten around to it. Pure kyanite is colorless, but most kyanite is sky blue. In fact, the name “kyanite” comes from the Greek word kyanos, which means “blue.” This common blue color comes from impurities such as iron and chromium. Other impurities produce such colors as: orange, brown, gray, pink, yellow, and green and sometimes they display color zoning. Kyanite’s crystals are long and flat and they have sharp edges. Kyanite actually has two different levels of hardness on the Mohs’ Scale. A mineral measuring only a 5 on the Mohs’ Scale will scratch a kyanite crystal if taken from top to bottom, but it will take a mineral measuring 7 or above to scratch it when taken from side to side!
     Kyanite is used to make things like fire brick, brake pads and electrical porcelains for cars, floor and wall tiles, and molds for metal casting. Kyanite is also used as a gemstone. The mineral is found all over the world, but some of the best sources are: Kenya, Zimbabwe, Tanzania, Russia, Switzerland, Ukraine, Brazil, India, the Canadian provinces of Quebec and Manitoba, and much of the United States’ Appalachian Region.
     Kyanite is somewhat or a rarity among minerals. Not because it can’t be found in many places, it’s quite common in that way. No, kyanite is rare because of its properties. After all how many other minerals have different harness values depending on the direction that you scratch them?