Kyanite is a distinctive aluminosilicate mineral, recognized for its typically blue hue that can range from pale to deep shades, though it also appears in white, gray, green, or orange variations. This mineral frequently forms as elongated, blade-like crystals. Beyond its use in jewelry and ornamental pieces, kyanite is also employed in industrial applications, including ceramics and refractory materials, due to its heat resistance. A unique characteristic of kyanite is its anisotropic hardness, meaning its hardness varies depending on the direction across the crystal.
Kyanite’s Interaction with Water
Kyanite’s structural properties make it sensitive to water, especially with prolonged exposure. While brief, incidental contact, such as splashes, might not cause immediate damage, extended immersion or frequent wetting is generally not recommended.
Along the length of its bladed crystals, kyanite typically has a Mohs hardness of 4 to 5.5, which is relatively soft. However, when measured across its width, the hardness increases to 6 to 7.5. This variability in hardness means that some areas are more susceptible to physical alteration.
Kyanite also possesses a perfect cleavage in one direction and good cleavage in another, which are planes where the crystal structure is weaker and prone to splitting. Water, particularly over time, can penetrate and exploit these natural cleavage planes. This interaction can dull the stone’s luster, cause a loss of vibrant appearance, or result in fracturing or flaking, especially in raw or less polished specimens. Therefore, soaking kyanite is advised against due to the risk of damage. Raw kyanite is particularly vulnerable, as water can cause it to flake, dissolve, or rust.
Caring for Your Kyanite
Proper care helps preserve the appearance and integrity of kyanite, especially given its water sensitivity. For cleaning, it is best to use a soft, dry cloth to gently wipe the stone. If a more thorough cleaning is needed, a slightly damp cloth with mild soap and lukewarm water can be used, but the kyanite should be dried immediately and thoroughly. Brief rinsing under cool, running water is an option for some kyanite pieces, but caution is necessary for fragile or thin specimens, which could break.
Several cleaning methods and conditions should be avoided to prevent damage to kyanite. Ultrasonic cleaners, which use vibrations, can cause internal fractures or crazing within the stone. Similarly, steam cleaners are not suitable as they can harm the delicate structure. Exposure to harsh household chemicals, such as bleach or ammonia, or contact with pool water and personal care products can lead to etching or discoloration of the mineral’s surface. Kyanite should also be protected from extreme temperature changes, which can compromise its stability.
Storing kyanite correctly is also important; it should be kept in a soft-lined box or pouch, separated from harder materials to prevent scratches, and in a dust-free environment. Prolonged exposure to direct sunlight may cause the stone’s color to fade, and high humidity can lead to rusting.