Kyanite Properties, Meaning, Facts and Photos
What is Kyanite?
Kyanite is a relatively rare aluminium silicate mineral composed of aluminium, silicon and oxygen. It occurs in metamorphic rocks, particularly those that have changed due to heat and pressure.
The name 'Kyanite' comes from the Greek word 'kyanos,' meaning 'deep blue.'
Kyanite is allochromatic, meaning it can occur in various colours due to trace impurities. Although best known for its long, slender blue crystals, other colours include blue-green, brown, orange, black, shades of grey, and colourless.
Kyanite that's colourless or blue-green is less common. Brown comes from iron, while iron and manganese turn kyanite orange. Black and other darker colours are believed to come from graphite, magnetite, ilmenite, or annite.
Despite being brittle, kyanite is widely used in industry because of its exceptional hardness. Its crystals are also known for their ability to withstand high temperatures, making them a popular choice for refractory materials.
Refractory materials are resistant to heat, so are often used in high-temperature applications. When kyanite is heated, it expands and, in some cases, can double in size.
In the manufacture of certain refractory products, particularly those that shrink during heating, kyanite is added to the raw material to maintain the volume of the finished product.
Another reason kyanite is widely used in industry is its high melting point and good thermal conductivity.
In addition to its heat-resistant properties, kyanite is highly resistant to corrosion and wear, making it a durable and long-lasting material.
Kyanite crystals are translucent and often exhibit a natural vitreous lustre. They're known for being pleochroic and for having a variation in hardness. Whilst most minerals have one hardness, kyanite and a few others have two.
When tested lengthwise, kyanite crystals grade 4.5 to 5 on the Mohs scale of hardness. However, when tested across the width, they grade 6 to 7. This characteristic, plus the fact that kyanite is brittle, makes it a difficult mineral to cut.
Kyanite often forms long, slender, bladed crystals, but they can also occur as a radiating mass, where crystals spread out from a centre point.
Kyanite is not often used as a gemstone, but when it is, it tends to be faceted. It's common for stones to have a 'scratchy' appearance even after being polished and/or other minor surface imperfections.
The finest-grade blue kyanite has been known to rival the colour of sapphire.
Kyanite is found in the United States, Brazil, Switzerland, Russia, Serbia, India and Kenya. Fine gem-grade crystals have also been found in Nepal, although exact quantities are unknown.
Article Photos
Both photos in our article are clickable and redirect to the original images. Photos are courtesy of Stan Celestian.
