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Kyanite is a challenging mineral to cut because it has two distinctly different hardnesses. Kyanite crystals are typically long, narrow blades. They have a hardness of about 4.5 parallel to their length but a hardness of 6.5 to 7.0 across the width of the blade. Skilled cutters are needed to work these stones.

Kyanite is a gemstone that you will rarely encounter in the typical jewelry store. Most people have not heard of kyanite, as it is infrequently used in jewelry. It is an “exotic” gem. Perhaps that is what makes it so interesting? If you are interested in kyanite as a gemstone or in jewelry, the best place to find…

Kyanite, unlike most other minerals, can expand significantly when heated. Depending upon particle size, temperatures, and heating conditions, kyanite can expand to up to twice its original volume when heated. This expansion is predictable. In the manufacture of certain refractory products, specific amounts of kyanite are added to the raw material (which shrinks during heating)…

Kyanite’s heat resistance and hardness make it an excellent material for use in the manufacture of grinding wheels and cutting wheels. It is not used as the primary abrasive; instead, it is used as part of the binding agent that holds the abrasive particles together in the shape of a wheel.

Kyanite has properties that make it exceptionally well suited for the manufacture of a high-refractory-strength porcelain – a porcelain that holds its strength at very high temperatures. A familiar use of this type of porcelain is the white porcelain insulator on a spark plug. Kyanite is also used in some of the more common forms…

Kyanite is used to manufacture a wide range of products. An important use is in the manufacture of refractory products such as the bricks, mortars, and kiln furniture used in high-temperature furnaces. For foundries, the molds that are used for casting high-temperature metals are often made with kyanite. Kyanite is also in products used in…

Three minerals have a chemical composition of Al2SiO5. These are kyanite, andalusite, and sillimanite. Kyanite is the high-pressure polymorph, sillimanite forms at high temperature, and andalusite is the low-pressure polymorph. Physical Properties of Kyanite Chemical Classification Silicate Color Blue, white, gray, green, colorless Streak White, colorless Luster Vitreous, pearly Diaphaneity Transparent to translucent Cleavage Perfect in…

Kyanite specimens have a variable hardness. The long crystals have a Mohs hardness of about 4.5 to 5 if tested parallel to the length of a crystal, and a hardness of 6.5 to 7 if tested across the short dimension of a crystal. The mineral was once commonly called “disthene” which means “two strengths.”

Kyanite is a mineral found mainly in metamorphic rocks. It most often forms from the high-pressure alteration of clay minerals during the metamorphism of sedimentary rocks. It is found in the schists and gneisses of regionally metamorphosed areas and less often in quartzite or eclogite. Kyanite’s typical habit is a bladed crystal, although it sometimes occurs as radiating masses of crystals. Kyanite is often associated with…