Chemical Formula Al2SiO5
Hardness 4.5 – 7
Crystal System Triclinic
Refractive Index 1.71 – 1.73
SG 3.5 – 3.7
Transparency Transparent to translucent
Double Refraction -0.015
Mineral Class Kyanite
The blue color of Kyanite is usually inconsistent in crystals, with lighter and darker color zones and streaks often present. This can make cutting a crystal into a gem a challenge as color consistency in a gem is more desirable. Kyanite can also form in other colors such as colorless, white, green, yellow, and orange, but these other colors are uncommon, and generally only the blue color is used as a gemstone. Kyanite gemstones rarely display asterism in cabochons.
Kyanite is the most anisotropic of all gemstones, meaning its hardness differs on its horizontal and vertical sides. It is fairly soft when cut parallel to the long axis of the crystal, with a hardness of only 4.5 to 5.5. On the shorter side of the crystal the hardness is 6 to 7. This unique hardness property plays a role when cutting a crystal. Care must also be exercised not to scratch Kyanite gems as they are fairly soft for a gemstone (specifically on their horizontal axis).
Kyanite is used as a minor blue gemstone. It is can be cut into various gemstone facets and cabochons. In jewelry, its use is limited mostly to earrings and pendants.
CyaniteKyanite gemstones are not heated or enhanced.Traditional Kyanite sources of gem crystals include Brazil, Cambodia, Burma (Myanmar), Switzerland, Russia, Kenya, and the U.S. (North Carolina, Connecticut, and Maine). A relatively recent discovery of Kyanite in Nepal in 1995 has produced gem crystals of Kyanite of exceptional color and transparency.Sapphire can appear similar to Kyanite, but can be distinguished by its greater hardness. Iolite is visibly pleochroic, and Tanzanite is usually lighter in color and has a more purplish hue. Labradorite is an important feldspar gemstone. It often displays a beautiful iridescent play of colors, which can move as the stone is rotated. Labradorite gemstones usually have a dark base color with metallic-looking color plays of blue, green, yellow, and red. This iridescent effect is commonly known as labradorescence, and is named after this stone. It is caused by internal fractures that reflect light back and forth, dispersing it into different colors.
Kyanite TREATMENTS AND ENHANCEMENTS