Kyanite

Amazing beauty of the sky-blue crystals of kyanite with nothing to confuse. The most reliable diagnostic feature of this mineral - hardness: steel knife easily scratched crystal along the extension, but not across.
The name of the mineral comes from the Greek word "kianos", which means "blue." The second common name Kyanite - kyanite - indicates a significant difference in the hardness of this mineral in different directions. Along the crystal relative hardness on the Mohs scale is 4, and across - 6.5-7. The absolute values ​​of microhardness in kyanite vary by eight times.
Buttresses CRYSTALS
Kyanite forms a transparent or translucent crystals prismatic, flattened shape. In appearance they resemble the boards, so called buttresses.
Kyanite usually painted in a nice blue-blue color, characteristic for this mineral. As a rule, the color of the crystals is not uniform: the brighter spots or stripes are combined with less colored areas. More rarely kyanite may be green or yellow, very rarely - a colorless, black.
BORN UNDER PRESSURE
In gneisses and schists kyanite acts as rock-forming mineral. These rocks were formed during regional metamorphism of rocks rich in aluminum high pressure in the atmosphere. In other words, kyanite crystallized deep in the earth's crust. It is associated with mica, corundum, tourmaline, and forms with staurolite correct fusion of brown-brown. Occasionally kyanite occurs in pegmatites and quartz veins.
Ore of aluminum and precious
Transparent crystals of kyanite prized in jewelry. The high content of alumina and is widespread in nature can be used as a valuable mineral ore.
Did you know that ...
Faceted blue kyanite looks like a sapphire, but has a lower hardness. Transparent blue kyanite can be confused with aquamarine. Jewelers distinguish these stones in density and refractive index. As part of kyanite 63.1% fall in alumina (A12O3). The same amount of this component include andalusite and sillimanite.
THE APPLICATION
From ores kyanite, sillimanite and andalusite after high firing are mullite. This substance is stable to acids and bases, high fire resistance and mechanical strength. Not surprisingly, one of the main industrial applications Kyanite - manufacture of ceramic and refractory products. It also is used to make insulation and chemically inert materials are not afraid even of hydrofluoric acid.
COMPLEX CUT
Kyanite known heterogeneity of hardness in different directions: it varies from 4 to 7 on the Mohs scale. In addition, this mineral is perfect cleavage in one direction. The combination of these properties - a difficult test for jewelers, granyaschih abrasive crystals and kyanite, Still a good master to achieve impressive results, playing with form and color. Depending on the crystallographic orientation of kyanite color changes from violet-blue to colorless or cornflower blue. In some crystals, color varies from yellow-green to green.
Hardness
Vary greatly in two directions hardness - a unique feature of kyanite. However, a number of other minerals hardness values ​​also vary depending on the orientation of the crystal. For example, the diamond has a hardness of each face is directly dependent on the concentration of atoms in the filed route. Jewelers use this property of diamond to best highlight its color and shine, while reducing consumption of the precious stone.
Where seen kyanite
The mineral is widely distributed in the earth's crust and is found throughout the world. The largest of its deposits are in Brazil, the United States (North Carolina, Georgia), and Switzerland. Russia has significant reserves of kyanite are known in the Kola Peninsula, Karelia and the Urals.